Renewable Energy Commercialization

Renewable energy commercialization involves the diffusion of three generations of technologies dating back more than 100 years. First-generation technologies, which are already mature and economically competitive, include biomass, hydroelectricity, geothermal power and heat. Second-generation technologies are market-ready and are being deployed at the present time; they include solar heating, photovoltaic, wind power and modern forms of bioenergy. Third-generation technologies require continued R&D efforts in order to make large contributions on a global scale and include advanced biomass gasification, bio refinery technologies, solar thermal power stations, hot-dry-rock geothermal power, and ocean energy.

While there are many non-technical barriers to the widespread use of renewable, some 65 countries now have targets for their own renewable energy futures, and have enacted wide-ranging public policies to promote renewable. Climate change concerns are driving increasing growth in the renewable energy industries and investment capital flowing into renewable energy reached a record US$77 billion in 2007. Leading renewable energy companies include: Enercon, Gamesa, GE Energy, Q-Cells, Sharp Solar, SunOpta, and Vestas.

Overview

The International Energy Agency (IEA) has defined three generations of renewable energy technologies, reaching back over 100 years:

• First-generation technologies emerged from the industrial revolution at the end of the 19th century and include hydropower, biomass combustion, geothermal power and heat. These technologies are quite widely used.

• Second-generation technologies include solar heating and cooling, wind power, modern forms of bioenergy, and solar photovoltaics. These are now entering markets as a result of research, development and demonstration (RD&D) investments since the 1980s. Initial investment was prompted by energy security concerns linked to the oil crises of the 1970s but the enduring appeal of these technologies is due, at least in part, to environmental benefits. Many of the technologies reflect significant advancements in materials.

• Third-generation technologies are still under development and include advanced biomass gasification, biorefinery technologies, concentrating solar thermal power, hot-dry-rock geothermal power, and ocean energy. Advances in nanotechnology may also play a major role.

First-generation technologies are well established, second-generation technologies are entering markets, and third-generation technologies heavily depend on long-term RD&D commitments, where the public sector has a role to play.

Renewable energy technologies are essential contributors to the energy supply portfolio, as they contribute to world energy security, reduce dependency on fossil fuels, and provide opportunities for mitigating greenhouse gases. The IEA estimates that nearly 50% of global electricity supplies will need to come from renewable energy sources in order to halve CO2 emissions by 2050 and minimize significant, irreversible climate change impacts.

First-generation technologies

First-generation technologies are widely used in locations with abundant resources. Their future use depends on the exploration of the remaining resource potential, particularly in developing countries, and on overcoming challenges related to the environment and social acceptance.

Biomass

Biomass for heat and power is a fully mature technology which offers a ready disposal mechanism for municipal, agricultural, and industrial organic wastes. However, the industry has remained relatively stagnant over the decade to 2007, even though demand for biomass (mostly wood) continues to grow in many developing countries. One of the problems of biomass is that material directly combusted in cook stoves produces pollutants, leading to severe health and environmental consequences, although improved cook stove programmes are alleviating some of these effects. First-generation biomass technologies can be economically competitive, but may still require deployment support to overcome public acceptance and small-scale issues.

Hydroelectricity

Hydroelectric plants have the advantage of being long-lived and many existing plants have operated for more than 100 years. Hydro power is also an extremely flexible technology from the perspective of power grid operation. Large hydro power provides one of the lowest cost options in today’s energy market, even compared to fossil fuels and there are no harmful emissions associated with plant operation.

However, there are several significant social and environmental disadvantages of large-scale hydroelectric power systems: dislocation of people living where the reservoirs are planned, release of significant amounts of carbon dioxide and methane during construction and flooding of the reservoir, and disruption of aquatic ecosystems and bird life. Hydroelectric power is now more difficult to site in developed nations because most major sites within these nations are either already being exploited or may be unavailable for these environmental reasons. The areas of greatest hydroelectric growth are the growing economies of Asia. China is the development leader; however, other Asian nations are also expanding hydro power.

There is a strong consensus now that countries should adopt an integrated approach towards managing water resources, which would involve planning hydro power development in co-operation with other water-using sectors.

Geothermal power and heat

Geothermal power plants can operate 24 hours per day, providing baseload capacity, and the world potential capacity for geothermal power generation is estimated at 85 GW over the next 30 years. However, geothermal power is accessible only in limited areas of the world. The costs of geothermal energy have dropped substantially from the systems built in the 1970s.

Geothermal heat generation can be competitive in many countries producing geothermal power, or in other regions where the resource is of a lower temperature.

Second-generation technologies

Markets for second-generation technologies have been strong and growing over the past decade, and these technologies have gone from being a passion for the dedicated few to a major economic sector in countries such as Germany, Spain, the United States, and Japan. Many large industrial companies and financial institutions are involved and the challenge is to broaden the market base for continued growth worldwide.

Solar Heating

Solar heating systems are a well known second-generation technology and generally consist of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage, and a reservoir or tank for heat storage. The systems may be used to heat domestic hot water, swimming pools, or homes and businesses. The heat can also be used for industrial process applications or as an energy input for other uses such as cooling equipment. In many warmer climates, a solar heating system can provide a very high percentage (50 to 75%) of domestic hot water energy. An early solar heating boom took place during the 1940s in the United States, during which period institutional support for solar research and energy conservation measures imposed during World War II fueled significant advances in solar technology, which went as far as the development of a prototype prefabricated solar-heated home. A few proponents of this technology saw it as a clean alternative to polluting fuels, but the great majority of advocates, researchers, and investors saw it as a solution to high energy costs during the war; when those conditions changed and the 1950s ushered in a period of record low energy prices, interest rapidly waned, and the commercial development of solar heating systems was postponed to a later decade.

Photovoltaics

Photovoltaic (PV) cells, also called solar cells, convert light into electricity. In the 1980s and early 1990s, most photovoltaic modules were used to provide Remote Area Power Supply, but from around 1995, industry efforts have focused increasingly on developing building integrated photovoltaics and photovoltaic power stations for grid connected applications. Currently the largest photovoltaic power plant in North America is the Nellis Solar Power Plant (15 MW). There is a proposal to build a Solar power station in Victoria, Australia, which would be the world's largest PV power station, at 154 MW.^[17][18] Other large photovoltaic power stations, which are under construction, include the Girassol solar power plant (62 MW), and the Waldpolenz Solar Park (40 MW).

Annual production of photovoltaics reached 3,800 megawatts worldwide in 2007, an increase of 50 percent over 2006. At the end of 2007, according to preliminary data, cumulative global production was 12,400 megawatts. Photovoltaic production has been doubling every two years, increasing by an average of 48 percent each year since 2002, making it the world’s fastest-growing energy technology. The top five photovoltaic producing countries are Japan, China, Germany, Taiwan, and the USA.

Wind power

Some of the second-generation renewable, such as wind power, have high potential and have already realized relatively low production costs. As of April 2008, worldwide wind farm capacity was 100,000 megawatts (MW), and wind power produced some 1.3% of global electricity consumption, accounting for approximately 18% of electricity use in Denmark, 9% in Spain, and 7% in Germany. However, it may be difficult to site wind turbines in some areas for aesthetic or environmental reasons.

United States is an important growth area and 2008 American Wind Energy Association figures show that installed U.S. wind power capacity has reached 21,000 MW. Some of the largest wind farms operating in the U.S. are: Horse Hollow Wind Energy Center, TX (736 MW); Maple Ridge Wind Farm, NY (322 MW); Stateline Wind Project, OR & WA (300 MW); King Mountain Wind Farm, TX (281 MW); and Sweetwater Wind Farm, TX (264 MW).

Modern forms of Bioenergy

Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane, and ethanol now provides 18 percent of the country's automotive fuel. As a result of this and the exploitation of domestic deep water oil sources, Brazil, which for years had to import a large share of the petroleum needed for domestic consumption, recently reached complete self-sufficiency in liquid fuels.

Production and use of ethanol has been stimulated through: (1) low-interest loans for the construction of ethanol distilleries; (2) guaranteed purchase of ethanol by the state-owned oil company at a reasonable price; (3) retail pricing of neat ethanol so it is competitive if not slightly favorable to the gasoline-ethanol blend; and (4) tax incentives provided during the 1980s to stimulate the purchase of neat ethanol vehicles. Guaranteed purchase and price regulation were ended some years ago, with relatively positive results. In addition to these other policies, ethanol producers in the state of São Paulo established a research and technology transfer center that has been effective in improving sugar cane and ethanol yields.

Most cars on the road today in the U.S. can run on blends of up to 10% ethanol, and motor vehicle manufacturers already produce vehicles designed to run on much higher ethanol blends. Ford, DaimlerChrysler, and GM are among the automobile companies that sell “flexible-fuel” cars, trucks, and minivans that can use gasoline and ethanol blends ranging from pure gasoline up to 85% ethanol (E85). By mid-2006, there were approximately six million E85-compatible vehicles on U.S. roads. The challenge is to expand the market for biofuels beyond the farm states where they have been most popular to date. Flex-fuel vehicles are assisting in this transition because they allow drivers to choose different fuels based on price and availability. The Energy Policy Act of 2005, which calls for 7.5 billion gallons of biofuels to be used annually by 2012, will also help to expand the market.

It should also be noted that the growing ethanol and biodiesel industries are providing jobs in plant construction, operations, and maintenance, mostly in rural communities. According to the Renewable Fuels Association, the ethanol industry created almost 154,000 U.S. jobs in 2005 alone, boosting household income by $5.7 billion. It also contributed about $3.5 billion in tax revenues at the local, state, and federal levels.

Third-generation technologies

Third-generation renewable energy technologies are still under development and include advanced biomass gasification, biorefinery technologies, solar thermal power stations, hot-dry-rock geothermal power, and ocean energy. Third-generation technologies are not yet widely demonstrated or have limited commercialization. Many are on the horizon and may have potential comparable to other renewable energy technologies, but still depend on attracting sufficient attention and RD&D funding.

New bioenergy technologies

According to the International Energy Agency, new bioenergy (biofuel) technologies being developed as of 2006, notably cellulosic ethanol biorefineries, could allow biofuels to play a much bigger role in the future than organizations such as the IEA previously thought. Cellulosic ethanol can be made from plant matter composed primarily of inedible cellulose fibers that form the stems and branches of most plants. Crop residues (such as corn stalks, wheat straw and rice straw), wood waste, and municipal solid waste are potential sources of cellulosic biomass. Dedicated energy crops, such as switchgrass, are also promising cellulose sources that can be sustainably produced in many regions of the United States.

Solar thermal power stations

Solar thermal power stations have been successfully operating in California commercially since the late 1980s, including the largest solar power plant of any kind, the 350 MW Solar Energy Generating Systems. Nevada Solar One is another 64 MW plant which has recently opened. Other parabolic trough power plants being proposed are two 50 MW plants in Spain, and a 100 MW plant in Israel.

Ocean energy

In terms of ocean energy, another third-generation technology, Portugal has the world's first commercial wave farm, the Aguçadora Wave Park, opened in 2008. The first stage of the farm uses three Pelamis P-750 machines generating a total of 2.25 MW. The cost of the farm is put at 8.5 million euro. A second phase of the project is now planned to increase the installed capacity from 2.25 MW to 21 MW using a further 25 Pelamis machines. Funding for a wave farm in Scotland was announced in February 2007 by the Scottish Executive, at a cost of over 4 million pounds, as part of a £13 million funding packages for ocean power in Scotland. The farm will be the world's largest with a capacity of 3 MW generated by four Pelamis machines.

In 2007, the world's first commercial tidal power station was installed in the narrows of Strangford Lough in Ireland. The 1.2 megawatt underwater tidal electricity generator, part of Northern Ireland's Environment & Renewable Energy Fund scheme, takes advantage of the fast tidal flow (up to 4 metres per second) in the lough. Although the generator is powerful enough to power a thousand homes, the turbine has minimal environmental impact, as it is almost entirely submerged, and the rotors pose no danger to wildlife as they turn quite slowly.

Enhanced geothermal systems

Enhanced geothermal systems, also known as hot dry rock geothermal, utilise new techniques to exploit resources that would have been uneconomical in the past. These systems are still in the research phase, and require additional R&D for new and improved approaches, as well as to develop smaller modular units that will allow economies of scale at the manufacturing level. Further government-funded research and close collaboration with industry will help to make exploitation of geothermal resources more economically attractive for investors.

Nanotechnology thin-film solar panels

Solar power panels that use nanotechnology, which can create circuits out of individual silicon molecules, may cost half as much as traditional photovoltaic cells, according to executives and investors involved in developing the products. Nanosolar has secured more than $100 million from investors to build a factory for nanotechnology thin-film solar panels. The company expects the factory to open in 2010 and produce enough solar cells each year to generate 430 megawatts of power.

Renewable energy industry

By mid-2007, some 140 publicly-traded renewable energy companies worldwide (or renewable energy divisions of major companies) each had a market capitalization greater than $40 million. The estimated total market capitalization of these companies and divisions was more than $100 billion in mid-2007.

In 2000, venture capital (VC) investment in renewable energy was about 1% of total VC investment. In 2007 that figure was closer to 10%, with solar power alone making up about 3% of the entire venture capital asset class of ~$33B. More than 60 start-ups have been funded by VCs in the last three years.

Wind power companies

Currently three quarters of global wind turbine sales come from only four turbine manufacturing companies: Vestas, Gamesa, Enercon, and GE Energy. Vestas, the market leader, has installed turbines in 60 countries. It is a Danish company which employs 14,000 people globally and, in 2003, merged with the Danish wind turbine manufacturer NEG Micon.

Gamesa, founded in 1976 with headquarters in Vitoria, Spain, is currently the world's second largest wind turbine manufacturer, after Vestas, and it is also a major builder of wind farms. Gamesa’s main markets are within Europe, the US and China. In 2006, Europe accounted for 65 percent of Gamesa’s sales, of which 40 percent were in Spain.

In 2004, German company Enercon installed a total of 1288 MW of wind power and had around 16% of the global market share. Enercon constructed production facilities in Brazil in 2006, and has extended its presence there, as well as in the more traditional markets of Germany, India, Austria, UK, Canada and the Netherlands.

GE Energy has installed over 5,500 wind turbines and 3,600 hydro turbines, and its installed capacity of renewable energy worldwide exceeds 160,000 MW. GE Energy bought out Enron Wind in 2002 and also has nuclear energy operations in its portfolio.

Photovoltaic companies

Q-Cells became the world's largest solar cell maker in 2007, producing nearly 400 MW of product. Longtime market leader Sharp Corporation found itself in second place with production of 370 MW in 2007, which the company blamed on a constrained supply of silicon. China's Suntech was close behind the leaders with more than 300 MW of output. Kyocera and its 200 MW output was a distant fourth in 2007.

Four new companies entered the top ranks in 2007. CdTe-cell maker First Solar was at fifth place, the only US-based and only thin-film supplier in the Top 10 companies. Asian players Motech Solar (Taiwan), Yingli Green Energy (China), and JA Solar Holdings (China/Australia) rounded out the Top 10 ranking, pushing aside some established players like Mitsubishi Electric, Schott, and BP Solar.

Other companies

SunOpta is located in Canada and was founded in 1973. Its operations are divided between SunOpta Food (organics), Opta Minerals, and SunOpta BioProcess (bioethanol). SunOpta's fastest growing business segment is the BioProcess Group, which is a leading developer of technology in the cellulosic ethanol market. SunOpta's BioProcess Group specializes in the design, construction and optimization of biomass conversion equipment and facilities. They have over 30 years experience delivering biomass solutions worldwide and use innovative technologies to produce cellulosic ethanol and cellulosic butanol. Raw materials include wheat straw, corn stover, grasses, oat hulls and wood chips.

Non-technical barriers to acceptance

There have been several recent reports which have identified a range of "non-technical barriers" to renewable energy use. These barriers are impediments which put renewable energy at a marketing, institutional, or policy disadvantage relative to other forms of energy. Key barriers include:

• Lack of government policy support, which includes the lack of policies and regulations supporting deployment of renewable energy technologies and the presence of policies and regulations hindering renewable energy development and supporting conventional energy development. Examples include subsidies for fossil-fuels, insufficient consumer-based renewable energy incentives, government underwriting for nuclear plant accidents, and complex zoning and permitting processes for renewable energy.
• Lack of information dissemination and consumer awareness.
• Higher capital cost of renewable energy technologies compared with conventional energy technologies.
• Difficulty overcoming established energy systems, which includes difficulty introducing innovative energy systems, particularly for distributed generation such as photovoltaics, because of technological lock-in, electricity markets designed for centralized power plants, and market control by established operators. As the Stern Review on the Economics of Climate Change points out:

National grids are usually tailored towards the operation of centralised power plants and thus favour their performance. Technologies that do not easily fit into these networks may struggle to enter the market, even if the technology itself is commercially viable. This applies to distributed generation as most grids are not suited to receive electricity from many small sources. Large-scale renewables may also encounter problems if they are sited in areas far from existing grids.

• Inadequate financing options for renewable energy projects, including insufficient access to affordable financing for project developers, entrepreneurs and consumers.
• Imperfect capital markets, which includes failure to internalize all costs of conventional energy (e.g., effects of air pollution, risk of supply disruption) and failure to internalize all benefits of renewable energy (e.g., cleaner air, energy security).
• Inadequate workforce skills and training, which includes lack of adequate scientific, technical, and manufacturing skills required for renewable energy production; lack of reliable installation, maintenance, and inspection services; and failure of the educational system to provide adequate training in new technologies.
• Lack of adequate codes, standards, utility interconnection, and net-metering guidelines.
• Poor public perception of renewable energy system aesthetics.
• Lack of stakeholder/community participation and co-operation in energy choices and renewable energy projects.

With such a wide range of non-technical barriers, there is no "silver bullet" solution to drive the transition to renewable energy. So ideally there is a need for several different types of policy instruments to complement each other and overcome different types of barriers.

A policy framework must be created that will level the playing field and redress the imbalance of traditional approaches associated with fossil fuels. The policy landscape must keep pace with broad trends within the energy sector, as well as reflecting specific social, economic and environmental priorities.

Education and renewable energy

To deal with these non-technical barriers to acceptance of renewable energy and also to address growing need for knowhow on non fossil fuel energy and issues like climate changes, several universities have set up special courses or research programs on renewable energy. In some cases universities from different countries have joined forces to form network to promote renewable energy. RES - The School for Renewable Energy Science in Iceland is an example of such international cooperation.

Public policy landscape

Public policy has a role to play in renewable energy commercialization because the free market system has some fundamental limitations. As the Stern Review points out:

In a liberalised energy market, investors, operators and consumers should face the full cost of their decisions. But this is not the case in many economies or energy sectors. Many policies distort the market in favour of existing fossil fuel technologies.

Lester Brown goes further and suggests that the market "does not incorporate the indirect costs of providing goods or services into prices, it does not value nature’s services adequately, and it does not respect the sustainable-yield thresholds of natural systems". It also favors the near term over the long term, thereby showing limited concern for future generations. Tax and subsidy shifting can help overcome these problems.

Shifting taxes

Tax shifting involves lowering income taxes while raising levies on environmentally destructive activities, in order to create a more responsive market. It has been widely discussed and endorsed by economists. For example, a tax on coal that included the increased health care costs associated with breathing polluted air, the costs of acid rain damage, and the costs of climate disruption would encourage investment in renewable technologies. Several Western European countries are already shifting taxes in a process known there as environmental tax reform, to achieve environmental goals.

A four-year plan adopted in Germany in 1999 gradually shifted taxes from labor to energy and, by 2001, this plan had lowered fuel use by 5 percent. It had also increased growth in the renewable energy sector, creating some 45,400 jobs by 2003 in the wind industry alone, a number that is projected to rise to 103,000 by 2010. In 2001, Sweden launched a new 10-year environmental tax shift designed to convert 30 billion kroner ($3.9 billion) of taxes on income to taxes on environmentally destructive activities. Other European countries with significant tax reform efforts are France, Italy, Norway, Spain, and the United Kingdom. Asia’s two leading economies, Japan and China, are considering the adoption of carbon taxes.

Shifting subsidies

Subsidies are not inherently bad as many technologies and industries emerged through government subsidy schemes. The Stern Review explains that of 20 key innovations from the past 30 years, only one of the 14 they could source was funded entirely by the private sector and nine were totally funded by the public sector. In terms of specific examples, the Internet was the result of publicly funded links among computers in government laboratories and research institutes. And the combination of the federal tax deduction and a robust state tax deduction in California helped to create the modern wind power industry.

But just as there is a need for tax shifting, there is also a need for subsidy shifting. Lester Brown has argued that "a world facing the prospect of economically disruptive climate change can no longer justify subsidies to expand the burning of coal and oil. Shifting these subsidies to the development of climate-benign energy sources such as wind, solar, biomass, and geothermal power is the key to stabilizing the earth’s climate."

Some countries are eliminating or reducing climate disrupting subsidies and Belgium, France, and Japan have phased out all subsidies for coal. Germany reduced its coal subsidy from $5.4 billion in 1989 to $2.8 billion in 2002, and in the process lowered its coal use by 46 percent. Germany plans to phase out this support entirely by 2010. China cut its coal subsidy from $750 million in 1993 to $240 million in 1995 and more recently has imposed a tax on high-sulfur coals.

While some leading industrial countries have been reducing subsidies to fossil fuels, most notably coal, the United States has been increasing its support for the fossil fuel and nuclear industries.

Renewable energy targets

Setting national renewable energy targets can be an important part of a renewable energy policy and these targets are usually defined as a percentage of the primary energy and/or electricity generation mix. For example, the European Union has prescribed an indicative renewable energy target of 12 per cent of the total EU energy mix and 22 per cent of electricity consumption by 2010. National targets for individual EU Member States have also been set to meet the overall target. Other developed countries with defined national or regional targets include Australia, Canada, Japan, New Zealand, Norway, Switzerland, and some US States.

National targets are also an important component of renewable energy strategies in some developing countries. Developing countries with renewable energy targets include China, India, Korea, Indonesia, Malaysia, the Philippines, Singapore, Thailand, Brazil, Israel, Egypt, Mali, and South Africa. The targets set by many developing countries are quite modest when compared with those in some industrialized countries.

Renewable energy targets in most countries are indicative and nonbinding but they have assisted government actions and regulatory frameworks. The United Nations Environment Program has suggested that making renewable energy targets legally binding could be an important policy tool to achieve higher renewable energy market penetration.

Recent developments

A number of events in 2006 pushed renewable energy up the political agenda, including the US mid-term elections in November, which confirmed clean energy as a mainstream issue. Also in 2006, the Stern Review made a strong economic case for investing in low carbon technologies now, and argued that economic growth need not be incompatible with cutting energy consumption. According to a trend analysis from the United Nations Environment Programme, climate change concerns coupled with recent high oil prices and increasing government support are driving increasing rates of investment in the renewable energy and energy efficiency industries.

Investment capital flowing into renewable energy reached a record US$77 billion in 2007, with the upward trend continuing in 2008. The OECD still dominates, but there is now increasing activity from companies in China, India and Brazil. Chinese companies were the second largest recipient of venture capital in 2006 after the United States. In the same year, India was the largest net buyer of companies abroad, mainly in the more established European markets.

Renewable energy (and energy efficiency) are no longer niche sectors that are promoted only by governments and environmentalists. The increased levels of private investment and the fact that much of the capital is coming from more conventional financial factors suggest that sustainable energy options are now becoming mainstream. A recent report from Helmut Kaiser Consultancy of Zurich states that the generation and storage of renewable energy will be the fastest growing sector in energy market over the next 20 years. The international law firm of Thompson & Knight LLP has launched a Climate Change and Renewable Energy Practice Group, consisting of 26 attorneys. The Ernst & Young "Country Attractiveness Indices" provide scores (out of 100) for national renewable energy markets, renewable energy infrastructures and their suitability for individual technologies.

Sustainable energy

Moving towards energy sustainability will require changes not only in the way energy is supplied, but in the way it is used, and reducing the amount of energy required to deliver various goods or services is essential. Opportunities for improvement on the demand side of the energy equation are as rich and diverse as those on the supply side, and often offer significant economic benefits.

Renewable energy and energy efficiency are said to be the “twin pillars” of sustainable energy policy. Any serious vision of a sustainable energy economy requires commitments to both renewables and efficiency. The American Council for an Energy-Efficient Economy has explained that both resources must be developed in order to stabilize and reduce carbon dioxide emissions:

Efficiency is essential to slowing the energy demand growth so that rising clean energy supplies can make deep cuts in fossil fuel use. If energy use grows too fast, renewable energy development will chase a receding target. Likewise, unless clean energy supplies come online rapidly, slowing demand growth will only begin to reduce total emissions; reducing the carbon content of energy sources is also needed.

The IEA has stated that renewable energy and energy efficiency policies should be viewed as complementary tools for the development of a sustainable energy future, instead of being developed in isolation.

Efficient Energy Use

Efficient energy use, sometimes simply called energy efficiency, is using less energy to provide the same level of energy service. An example would be insulating a home to use less heating and cooling energy to achieve the same temperature. Another example would be installing fluorescent lights and/or skylights instead of incandescent lights to attain the same level of illumination. Efficient energy use is achieved primarily by means of a more efficient technology or process rather than by changes in individual behaviour.

Energy efficient buildings, industrial processes and transportation could reduce the world's energy needs in 2050 by one third, and help controlling global emissions of greenhouse gases, according to the International Energy Agency.

Energy efficiency and renewable energy are said to be the “twin pillars” of sustainable energy policy.

However, there are many problems in calculating energy usage, and even bigger problems when discussing environmental impact.

Overview

Making homes, vehicles, and businesses more energy efficient is seen as a largely untapped solution to addressing global warming, energy security, and fossil fuel depletion. Many of these ideas have been discussed for years, since the 1973 oil crisis brought energy issues to the forefront. In the late 1970s, physicist Amory Lovins popularized the notion of a "soft energy path", with a strong focus on energy efficiency. Among other things, Lovins popularized the notion of negawatts -- the idea of meeting energy needs by increasing efficiency instead of increasing energy production.

Energy efficiency has proved to be a cost-effective strategy for building economies without necessarily growing energy consumption, as environmental business strategist Joel Makower has noted. For example, the state of California began implementing energy-efficiency measures in the mid-1970s, including building code and appliance standards with strict efficiency requirements. During the following years, California's energy consumption has remained approximately flat on a per capita basis while national U.S. consumption doubled. As part of its strategy, California implemented a three-step plan for new energy resources that puts energy efficiency first, renewable electricity supplies second, and new fossil-fired power plants last.

Still, efficiency often has taken a secondary position to new power generation as a solution to global warming in creating national energy policy. Some companies also have been reluctant to engage in efficiency measures, despite the often favorable returns on investments that can result. Lovins' Rocky Mountain Institute points out that in industrial settings, "there are abundant opportunities to save 70% to 90% of the energy and cost for lighting, fan, and pump systems; 50% for electric motors; and 60% in areas such as heating, cooling, office equipment, and appliances." In general, up to 75% of the electricity used in the U.S. today could be saved with efficiency measures that cost less than the electricity itself.

Other studies have emphasized this. A report published in 2006 by the McKinsey Global Institute, asserted that "there are sufficient economically viable opportunities for energy-productivity improvements that could keep global energy-demand growth at less than 1 percent per annum" -- less than half of the 2.2 percent average growth anticipated through 2020 in a business-as-usual scenario. Energy productivity -- which measures the output and quality of goods and services per unit of energy input -- can come from either reducing the amount of energy required to produce something, or from increasing the quantity or quality of goods and services from the same amount of energy.

The Vienna Climate Change Talks 2007 Report, under the auspices of the United Nations Framework Convention on Climate Change (UNFCCC), clearly shows "that energy efficiency can achieve real emission reductions at low cost."

Energy efficient appliances

Modern energy-efficient appliances, such as refrigerators, freezers, ovens, stoves, dishwashers, and clothes washers and dryers, use significantly less energy than older appliances. Current energy efficient refrigerators, for example, use 40 percent less energy than conventional models did in 2001. Modern power management systems also reduce energy usage by idle appliances by turning them off or putting them into a low-energy mode after a certain time. Many countries identify energy-efficient appliances using an Energy Star label.

Energy efficient building design

A building’s location and surroundings play a key role in regulating its temperature and illumination. For example, trees, landscaping, and hills can provide shade and block wind. In cooler climates, designing buildings with an east-west orientation to increase the number of south-facing windows minimizes energy use, by maximizing passive solar heating. Tight building design, including energy-efficient windows, well-sealed doors, and additional thermal insulation of walls, basement slabs, and foundations can reduce heat loss by 25 to 50 percent.

Dark roofs may become up to 70°F hotter than the most reflective white surfaces, and they transmit some of this additional heat inside the building. US Studies have shown that lightly colored roofs use 40 percent less energy for cooling than buildings with darker roofs. White roof systems save more energy in sunnier climates. Advanced electronic heating and cooling systems can moderate energy consumption and improve the comfort of people in the building.

Proper placement of windows and skylights and use of architectural features that reflect light into a building, can reduce the need for artificial lighting. Compact fluorescent lights use two-thirds less energy and last 6 to 10 times longer than incandescent light bulbs. Newer fluorescent lights produce a natural light, and in most applications they are cost effective, despite their higher initial cost, with payback periods as low as a few months. However, those ideals may not always be achieved in practice, because lifetime depends on the frequency of usage. In addition, CFLs emit UV light which can harm polymers and pigments. Thay also respind more slowly when switched on, so may represent a safety hazard in halls and stairways for example. Increased use of natural and task lighting have been shown by one study to increase productivity in schools and offices. However, fluorescent lighting can be harsh, and the flicker can induce migraine, so caution is needed when replacing incandescent lights.

Effecive energy-efficient building design can include the use of low cost Passive Infra Reds (PIRs) to switch-off lighting when areas are unnoccupied such as toilets, corridors or even office areas out-of-hours. In addition, lux levels can be monitored using daylight sensors linked to the building's lighting scheme to switch on/off or dim the lighting to pre-defined levels to take into account the natural light and thus reduce consumption. Building Management Systems (BMS) link all of this together in one centralised computer to control the whole building's lighting and power requirements.

Smart meters are slowly being adopted by the commerial sector to highlight to staff and for internal monitoring purposes the building's energy usage in a dynamic presentable format. The use of Power Quality Analysers can be introduced into an existing building to assess usage, harmonic distortion, peaks, swells and interruptions amongst others to ultimately make the building more energy-efficient.

Energy efficiency for industry

In industry, when electricity is generated, the heat which is produced as a by-product can be captured and used for process steam, heating or other industrial purposes. Conventional electricity generation is about 30 percent efficient, whereas combined heat and power (also called cogeneration) converts up to 90 percent of the fuel into usable energy.

Advanced boilers and furnaces can operate at higher temperatures while burning less fuel. These technologies are more efficient and produce fewer pollutants.

Over 45 percent of the fuel used by US manufacturers is burnt to make steam. The typical industrial facility can reduce this energy usage 20 percent (according to the US Department of Energy) by insulating steam and condensate return lines, stopping steam leakage, and maintaining steam traps.

Electric motors usually run on a constant flow of energy, but an adjustable speed drive can vary the motor’s energy output to match the load. This achieves energy savings ranging from 3 to 60 percent, depending on how the motor is used. Motor coils made of superconducting materials can also reduce energy losses. Motors may also benefit from voltage optimisation.

Many industries use compressed air for sand blasting, painting, or other tools. According to the US Department of Energy, optimizing compressed air systems by installing variable speed drives, along with preventive maintenance to detect and fix air leaks, can improve energy efficiency 20 to 50 percent.

Energy efficient vehicles

Using improved aerodynamics to minimize drag can increase vehicle fuel efficiency.

Reducing vehicle weight can significantly also improve fuel economy.

More advanced tires, with decreased tire to road friction and rolling resistance, can save gasoline. Fuel economy can be improved over three percent by keeping tires inflated to the correct pressure. Replacing a clogged air filter can improve a cars fuel consumption by as much as 10 percent.

Fuel efficient vehicles may reach twice the fuel efficiency of the average automobile. Cutting-edge designs, such as the diesel Mercedes-Benz Bionic concept vehicle have achieved a fuel efficiency as high as 84 miles per US gallon (2.8 L/100 km; 101 mpg_-imp), four times the current conventional automotive average.

Another growing trend in automotive efficiency is the rise of hybrid and electric cars. Hybrids, like the Toyota Prius, use regenerative braking to recapture energy that would dissipate in normal cars; the effect is especially pronounced in city driving. plug-in hybrids also have electrical plugs, which makes it possible to drive for limited distances without burning any gasoline; in this case, energy efficiency is dictated by whatever process (coal-burning, hydroelectric, etc) created the power. Plug-ins can typically drive for around 40 mile purely on electricity without recharging; if the battery runs low, a gas engine kicks in allowing for extended range. Finally, all-electric cars are also growing in popularity; the Tesla Roadster sports car is the only high-performance all-electric car currently on the market, and others are in design.

Energy conservation

Energy conservation is broader than energy efficiency in that it encompasses using less energy to achieve a lesser energy service, for example through behavioural change, as well as encompassing energy efficiency. Examples of conservation without efficiency improvements would be heating a room less in winter, driving less, or working in a less brightly lit room. As with other definitions, the boundary between efficient energy use and energy conservation can be fuzzy, but both are important in environmental and economic terms. This is especially the case when actions are directed at the saving of fossil fuels.

Sustainable energy

Energy efficiency and renewable energy are said to be the “twin pillars” of a sustainable energy policy. Both strategies must be developed concurrently in order to stabilize and reduce carbon dioxide emissions in our lifetimes. Efficient energy use is essential to slowing the energy demand growth so that rising clean energy supplies can make deep cuts in fossil fuel use. If energy use grows too rapidly, renewable energy development will chase a receding target. Likewise, unless clean energy supplies come online rapidly, slowing demand growth will only begin to reduce total carbon emissions; a reduction in the carbon content of energy sources is also needed. A sustainable energy economy thus requires major commitments to both efficiency and renewables.

Rebound effect

If the demand for energy services remains constant, improving energy efficiency will reduce energy consumption and carbon emissions. However, many efficiency improvements do not reduce energy consumption by the amount predicted by simple engineering models. This is because they make energy services cheaper, and so consumption of those services increase. For example, since fuel efficient vehicles make travel cheaper, consumers may choose to drive further and/or faster, thereby offsetting some of the potential energy savings. This is an example of the direct rebound effect.

Estimates of the size of the rebound effect range from roughly 5% to 40%. Rebound effects are smaller in mature markets where demand is saturated. The rebound effect is likely to be less than 30% at the household level and may be closer to 10% for transport. A rebound effect of 30% implies that improvements in energy efficiency should achieve 70% of the reduction in energy consumption projected using engineering models.

Since more efficient (and hence cheaper) energy will also lead to faster economic growth, there are suspicions that improvements in energy efficiency may eventually lead to even faster resource use. This was postulated by economists in the 1980's and remains a controversial hypothesis. Ecological economists have suggested that any cost savings from efficiency gains be taxed away by the government in order to avoid this outcome.

Energy Conservation

Energy conservation is the practice of decreasing the quantity of energy used. It may be achieved through efficient energy use, in which case energy use is decreased while achieving a similar outcome, or by reduced consumption of energy services. Energy conservation may result in increase of financial capital, environmental value, national security, personal security, and human comfort. Individuals and organizations that are direct consumers of energy may want to conserve energy in order to reduce energy costs and promote economic security. Industrial and commercial users may want to increase efficiency and thus maximize profit.

Introduction

Electrical energy conservation is an important element of energy policy. Energy conservation reduces the energy consumption and energy demand per capita, and thus offsets the growth in energy supply needed to keep up with population growth. This reduces the rise in energy costs, and can reduce the need for new power plants, and energy imports. The reduced energy demand can provide more flexibility in choosing the most preferred methods of energy production.

By reducing emissions, energy conservation is an important part of lessening climate change. Energy conservation facilitates the replacement of non-renewable resources with renewable energy. Energy conservation is often the most economical solution to energy shortages, and is a more environmentally benign alternative to increased energy production.

Energy Conservation By country

Energy Conservation in United States

The United States is currently the largest single consumer of energy. The U.S. Department of Energy categorizes national energy use in four broad sectors: transportation, residential, commercial, and industrial.

Energy usage in transportation and residential sectors (about half of U.S. energy consumption) is largely controlled by individual domestic consumers. Commercial and industrial energy expenditures are determined by businesses entities and other facility managers. National energy policy has a significant effect on energy usage across all four sectors.

Transportation

The transportation includes all vehicles used for personal or freight transportation. Of the energy used in this sector, approximately 65% is consumed by gasoline-powered vehicles, primarily personally owned. Diesel-powered transport (trains, merchant ships, heavy trucks, etc.) consumes about 20%, and air traffic consumes most of the remaining 15%.

The two oil supply crisis of the 1970s spurred the creation, in 1975, of the federal Corporate Average Fuel Economy (CAFE) program, which required auto manufacturers to meet progressively higher fleet fuel economy targets. The next decade saw dramatic improvements in fuel economy, mostly the result of reductions in vehicle size and weight which originated in the late 1970s, along with the transition to front wheel drive. These gains eroded somewhat after 1990 due to the growing popularity of sport utility vehicles, pickup trucks and minivans, which fall under the more lenient "light truck" CAFE standard.

In addition to the CAFE program, the U.S. government has tried to encourage better vehicle efficiency through tax policy. Since 2002, taxpayers have been eligible for income tax credits for gas/electric hybrid vehicles. A "gas-guzzler" tax has been assessed on manufacturers since 1978 for cars with exceptionally poor fuel economy. While this tax remains in effect, it currently generates very little revenue as overall fuel economy has improved. The gas-guzzler tax ended the reign of large cubic-inched engines from the musclecar era.

Another focus in gasoline conservation is reducing the number of miles driven. An estimated 40% of American automobile use is associated with daily commuting. Many urban areas offer subsidized public transportation to reduce commuting traffic, and encourage carpooling by providing designated high-occupancy vehicle lanes and lower tolls for cars with multiple riders. In recent years telecommuting has also become a viable alternative to commuting for some jobs, but in 2003 only 3.5% of workers were telecommuters. Ironically, hundreds of thousands of American and European workers have been replaced by workers in Asia who telecommute from thousands of miles away.

Fuel economy-maximizing behaviors also help reduce fuel consumption. Among the most effective are moderate (as opposed to aggressive) driving, driving at lower speeds, using cruise control, and turning off a vehicle's engine at stops rather than idling. A vehicle's gas mileage decreases rapidly highway speeds, normally above 55 miles per hour (though the exact number varies by vehicle). This is because aerodynamic forces are proportionally related to the square of an object's speed (when the speed is doubled, drag quadruples). According to the U.S. Department of Energy (DOE), as a rule of thumb, each 5 mph (8.0 km/h) you drive over 60 mph (97 km/h) is similar to paying an additional $0.30 per gallon for gas The exact speed at which a vehicle achieves it's highest efficiency varies based on the vehicle's drag coefficient, frontal area, surrounding air speed, and the efficiency and gearing of a vehicle's drive train and transmission.

Residential sector

The residential sector refers to all private residences, including single-family homes, apartments, manufactured homes and dormitories. Energy use in this sector varies significantly across the country, due to regional climate differences and different regulation. On average, about half of the energy used in U.S. homes is expended on space conditioning (i.e. heating and cooling).

The efficiency of furnaces and air conditioners has increased steadily since the energy crises of the 1970s. The 1987 National Appliance Energy Conservation Act authorized the Department of Energy to set minimum efficiency standards for space conditioning equipment and other appliances each year, based on what is "technologically feasible and economically justified". Beyond these minimum standards, the Environmental Protection Agency awards the Energy Star designation to appliances that exceed industry efficiency averages by an EPA-specified percentage.

Despite technological improvements, many American lifestyle changes have put higher demands on heating and cooling resources. The average size of homes built in the United States has increased significantly, from 1,500 sq ft (140 m²) in 1970 to 2,300 sq ft (210 m²) in 2005. The single-person household has become more common, as has central air conditioning: 23% of households had central air conditioning in 1978, that figure rose to 55% by 2001.

As furnace efficiency gets higher, there is limited room for improvement--efficiencies above 85% are now common. However, improving the building envelope through better or more insulation, advanced windows, etc., can allow larger improvements. The passive house approach produces superinsulated buildings that approach zero net energy consumption. Improving the building envelope can also be cheaper than replacing a furnace or air conditioner.

Even lower cost improvements include weatherization, which is frequently subsidized by utilities or state/federal tax credits, as are programmable thermostats. Consumers have also been urged to adopt a wider indoor temperature range (e.g. 65 °F (18 °C) in the winter, 80 °F (27 °C) in the summer).

One underutilized, but potentially very powerful means to reduce household energy consumption is to provide real-time feedback to homeowners so they can effectively alter their energy using behavior. Recently, low cost energy feedback displays, such as The Energy Detective or wattson, have become available. A study of a similar device deployed in 500 Ontario homes by Hydro One showed an average 6.5% drop in total electricity use when compared with a similarly sized control group.

Standby power used by consumer electronics and appliances while they are turned off accounts for an estimated 5 to 10% of household electricity consumption, adding an estimated $3 billion to annual energy costs in the USA. "In the average home, 75% of the electricity used to power home electronics is consumed while the products are turned off".

Home energy consumption averages

• Home heating systems, 30.7%
• Water heating, 13.5%
• Home cooling systems, 11.5%
• Lighting, 10.3%
• Refrigerators and freezers, 8.2%
• Home electronics, 7.2%
• Clothing and dish washers, 5.6% (includes clothes dryers, does not include hot water)
• Cooking, 4.7%
• Computers, 0.9%
• Other, 4.1% (includes small electrics, heating elements, motors, pool and hot tub heaters, outdoor grills, and natural gas outdoor lighting)
• Non end-user energy expenditure, 3.3%

Energy usage in some homes may vary widely from these averages. For example, milder regions such as the southern U.S. and Pacific coast of the USA need far less energy for space conditioning than New York City or Chicago. On the other hand, air conditioning energy use can be quite high in hot-arid regions (Southwest) and hot-humid zones (Southeast) In milder climates such as San Diego, lighting energy may easily consume up to 40% of total energy. Certain appliances such as a waterbed, hot tub, or pre-1990 refrigerator use significant amounts of electricity. However, recent trends in home entertainment equipment can make a large difference in household energy use. For instance a 50" LCD television (average on-time= 6 hours a day) may draw 300 Watts less than a similarly sized plasma system. In most residences no single appliance dominates, and any conservation efforts must be directed to numerous areas in order to achieve substantial energy savings. However, Ground, Air and Water Source Heat Pump systems are the more energy efficient, environmentally clean, and cost-effective space conditioning and domestic hot water systems available (Environmental Protection Agency), and can achieve reductions in energy consumptions of up to 69%.

Best building practices

Current best practices in building design, construction and retrofitting result in homes that are profoundly more energy conserving than average new homes. This includes insulation and energy-efficient windows and lighting. See Passive house, Superinsulation, Self-sufficient homes, Zero energy building, Earthship, MIT Design Advisor, Energy Conservation Code for Indian Commercial Buildings.

Smart ways to construct homes such that minimal resources are used to cooling and heating the house in summer and winter respectively can significantly reduce energy costs.

Commercial sector

The commercial sector consists of retail stores, offices (business and government), restaurants, schools and other workplaces. Energy in this sector has the same basic end uses as the residential sector, in slightly different proportions. Space conditioning is again the single biggest consumption area, but it represents only about 30% of the energy use of commercial buildings. Lighting, at 25%, plays a much larger role than it does in the residential sector. Lighting is also generally the most wasteful component of commercial use. A number of case studies indicate that more efficient lighting and elimination of over-illumination can reduce lighting energy by approximately fifty percent in many commercial buildings.

Commercial buildings can greatly increase energy efficiency by thoughtful design, with today's building stock being very poor examples of the potential of systematic (not expensive) energy efficient design (Steffy, 1997). Commercial buildings often have professional management, allowing centralized control and coordination of energy conservation efforts. As a result, fluorescent lighting (about four times as efficient as incandescent) is the standard for most commercial space, although it may produce certain adverse health effects. Potential health concerns can be mitigated by using newer fixtures with electronic ballasts rather than older magenetic ballasts. As most buildings have consistent hours of operation, programmed thermostats and lighting controls are common. However, too many companies believe that merely having a computer controlled Building automation system guarantees energy efficiency. As an example one large company in Northern California boasted that it was confident its state of the art system had optimized space heating. A more careful analysis by Lumina Technologies showed the system had been given programming instructions to maintain constant 24 hour temperatures in the entire building complex. This instruction caused the injection of nighttime heat into vacant buildings when the daytime summer temperatures would often exceed 90 °F (32 °C). This mis-programming was costing the company over $130,000 per year in wasted energy (Lumina Technologies, 1997). Many corporations and governments also require the Energy Star rating for any new equipment purchased for their buildings.

Solar heat loading through standard window designs usually leads to high demand for air conditioning in summer months. An example of building design overcoming this excessive heat loading is the Dakin Building in Brisbane, California, where fenestration was designed to achieve an angle with respect to sun incidence to allow maximum reflection of solar heat; this design also assisted in reducing interior over-illumination to enhance worker efficiency and comfort.

Recent advances include use of occupancy sensors to turn off lights when spaces are unoccupied, and photosensors to dim or turn off electric lighting when natural light is available. In air conditioning systems, overall equipment efficiencies have increased as energy codes and consumer information have begun to emphasise year round performance rather than just efficiency ratings at maximum output. Controllers that automatically vary the speeds of fans, pumps, and compressors have radically improved part-load performance of those devices. For space or water heating, electric heat pumps consume roughly half the energy required by electric resistance heaters. Natural gas heating efficiencies have improved through use of condensing furnaces and boilers, in which the water vapor in the flue gas is cooled to liquid form before it is discharged, allowing the heat of condensation to be used. In buildings where high levels of outside air are required, heat exchangers can capture heat from the exhaust air to preheat incoming supply air.

Industrial sector

The industrial sector represents all production and processing of goods, including manufacturing, construction, farming, water management and mining. Increasing costs have forced energy-intensive industries to make substantial efficiency improvements in the past 30 years. For example, the energy used to produce steel and paper products has been cut 40% in that time frame, while petroleum/aluminum refining and cement production have reduced their usage by about 25%. These reductions are largely the result of recycling waste material and the use of cogeneration equipment for electricity and heating.

Another example for efficiency improvements is the use of products made of High temperature insulation wool (HTIW) which enables predominantly industrial users to operate thermal treatment plants at temperatures between 800 and 1400°C. In these high-temperature applications, the consumption of primary energy and the associated CO₂ emissions can be reduced by up to 50% compared with old fashioned industrial installations. The application of products made of High temperature insulation Wool is becoming increasingly important against the background of the currently dramatic rising cost of energy.

The energy required for delivery and treatment of fresh water often constitutes a significant percentage of a region's electricity and natural gas usage (an estimated 20% of California's total energy use is water-related.) In light of this, some local governments have worked toward a more integrated approach to energy and water conservation efforts.

To conserve energy, some industries have begun using solar panels to heat their water.

Unlike the other sectors, total energy use in the industrial sector has declined in the last decade. While this is partly due to conservation efforts, it's also a reflection of the growing trend for U.S. companies to move manufacturing operations overseas.

Energy Conservation in United Kingdom

Energy conservation in the United Kingdom has been receiving increased attention over recent years. Key factors behind this are the Government's commitment to reducing carbon emissions, the projected 'energy gap' in UK electricity generation, and the increasing reliance on imports to meet national energy needs. Domestic housing and road transport are currently the two biggest problem areas.

The UK Government has jointly funded the Energy Saving Trust to promote energy conservation at a consumer, business and community level since 1993.

Issues with energy conservation

Critics and advocates of some forms of energy conservation make the following arguments:

• Standard economic theory suggests that technological improvements that increase energy efficiency will tend to increase, rather than reduce energy use. This is called the Jevons Paradox and it is said to occur in two ways. Firstly, increased energy efficiency makes the use of energy relatively cheaper, thus encouraging increased use. Secondly, increased energy efficiency leads to increased economic growth, which pulls up energy use in the whole economy. This does not imply that increased fuel efficiency is worthless. Increased fuel efficiency enables greater production and a higher quality of life.
• Some retailers argue that bright lighting stimulates purchasing. Health studies have demonstrated that headache, stress, blood pressure, fatigue and worker error all generally increase with the common over-illumination present in many workplace and retail settings (Davis, 2001), (Bain, 1997). It has been shown that natural daylighting increases productivity levels of workers, while reducing energy consumption.
• The use of telecommuting by major corporations is a significant opportunity to conserve energy, as many Americans now work in service jobs that enable them to work from home instead of commuting to work each day.
• Electric motors consume more than 60% of all electrical energy generated and are responsible for the loss of 10 to 20% of all electricity converted into mechanical energy.

Radioactive Contamination: Uranium in the Environment

Uranium in the environment, this page is about the science of uranium in the environment and in animals (including humans). The legal and social issues associated with uranium are discussed elsewhere. This page is a subpage of actinides in the environment.

Occurrence

From the land

Uranium is a naturally occurring element found in low levels within all rock, soil, and water. This is the highest-numbered element to be found naturally in significant quantities on earth. According to the United Nations the normal concentration of uranium in soil is 300 μg kg^-1 to 11.7 mg kg^-1. (United Nations Scientific Committee on the Effects of Atomic Radiation, 1993, Report to the General Assembly, with scientific annexes, New York)

It is considered to be more plentiful than antimony, beryllium, cadmium, gold, mercury, silver, or tungsten and is about as abundant as arsenic or molybdenum. It is found in many minerals including uraninite (most common uranium ore), autunite, uranophane, torbernite, and coffinite. Significant concentrations of uranium occur in some substances such as phosphate rock deposits, and minerals such as lignite, and monazite sands in uranium-rich ores (it is recovered commercially from these sources).

From the sea

Seawater contains about 3.3 parts per billion of uranium by weight (3.3 µg/kg) as uranium(VI) forms soluble carbonate complexes. The extraction of uranium from seawater has been considered as a means of obtaining the element.

Sources

Note that uranium is present in most soils at a low concentration, so the mere fact that a soil contains uranium does not mean that it has been artificially contaminated by uranium. While it is possible to use the isotope signature to identify the origin of uranium in a sample, for instance ²³⁶U is only formed in nuclear reactors fueled with ²³⁵U, but the ²³⁸U/²³⁵U ratio should be used with some caution. In Africa a set of natural nuclear fission reactors operated in one uranium rich area, the Oklo region in Gabon.

Metal

Munitions

The potential danger of exposure to depleted uranium has received widespread publicity because of the use of DU munitions in the 1991 Gulf War and 1999 Kosovo War, as well as current conflicts "A total of just over 290 metric tons of DU projectiles were fired by the US during the Gulf War (comapred [sic] to 9 tons in Kosovo and 3 tons in Bosnia and Herzegovina)". The potential long-term effects on people living in areas where DU munitions were used has also caused some concern.

Fragments from projectile DU munitions could cause substantial inhalation exposure risks in certain circumstances if the exposure was high. Studies by the University of Denver conclude that there is no risk of radiological effects on humans from DU munitions. However, there exists evidence that the density of uranium particles may lead to a variety of health effects. Uranium is a pyrophoric metal, which causes an incendiary affect in DU weapons, but also scatters the inert uranium 238 isotope into the air. DU exists normally in our environment. We eat it and breathe it in trace amounts on a daily basis. However, in areas where DU weapons have been used, uranium saturation can be dangerous. Because uranium is so heavy, the human body is poor at removing it. If inhaled in large amounts, it can cause respiratory arrest and is difficult to remove. If ingested, the kidneys filter uranium from the blood, and expel it in urine, but due to the difficulty of removing the large atom, it tends to accumulate more quickly than it is removed in areas of high concentrations of DU. Due to the weight of the atom, some believe this puts dangerous strain on kidney functions, and can lead to kidney failure.

Air crashes

Uranium metal, as depleted uranium, has been used in aircraft for trim weights in the past (although the practice has been discontinued), so after an air crash a release of uranium or its combustion products is possible.

Dispersion of uranium metal

• Uranium metal can disperse into the air and water, United Nations Environment Programme (UNEP) study says in part:

"The most important concern is the potential for future groundwater contamination by corroding penetrators (ammunition tips made out of DU). The munition tips recovered by the UNEP team had already decreased in mass by 10-15% in this way. This rapid corrosion speed underlines the importance of monitoring the water quality at the DU sites on an annual basis."

Combustion

Studies of depleted uranium aerosol exposure suggest that uranium combustion product particles would quickly settle out of the air and thus could not affect populations more than a few kilometers from target areas.

The U.S. has admitted that there have been over 100 "friendly fire" incidents in which members of the U.S. military have been struck by DU munitions, and that an unknown number have been exposed to DU via inhalation of combustion products from burning DU munitions.

Corrosion

It has been reported that the corrosion of uranium in a silica rich aqueous solution forms both uranium dioxide and uranium trioxide.

In pure water, schoepite {(UO₂)₈O₂(OH)₁₂.12(H₂O)} is formed in the first week and then after four months studtite {(UO₂)O₂·4(H₂O)} was formed. A report on the corrosion of uranium metal has been published by the Royal Society.

Uranium metal reacts with water to form hydrogen gas, this reaction forms uranium dioxide and 2 to 9% uranium hydride. It is important to note that the rate of corrosion due to water is far greater than that caused by oxygen at temperatures around 100 °C. At pH values below 2 the corrosion rate at 100 °C goes down greatly, while as pH values go from 7 upwards the corrosion rate declines. Gamma irradiation has little effect on the corrosion rate.

Oxygen gas inhibits the corrosion of uranium by water.

Compounds

From uranium mining

During the extraction of uranium ore and its processing, some releases of uranium occur. The releases of radium and other decay products of uranium are normally more important than the uranium in tailings ponds at the mines and ore processing centers.

From highly active waste in the form of glass

Note that while the vast majority of the uranium is removed by PUREX nuclear reprocessing, a small amount of uranium is left in the raffinate from the first cycle of the PUREX process. In addition due to the decay of the transplutonium minor actinides and the residual plutonium in the waste the concentration of uranium will increase on the waste. This will occur on a time scale of hundreds and thousands of years.

The waste from PUREX processing of used nuclear fuel is handled by vitrification, in the west it is converted into a borosilicate glass while in the former soviet bloc it is converted into a phosphate glass. The glass formed when placed in water will dissolve very slowly, according to the ITU it will require about 1 million years for 10% of the glass to dissolve in water.

From spent fuel

Spent uranium dioxide fuel is very insoluble in water, it is likely to release uranium (and fission products) even more slowly than borosilicate glass when in contact with water.

Behaviour in soil

A study has been done in the USA on the chemical form of uranium in soil, this was published by Benjamin C. Bostick, Scott Fendorf, Mark O. Barnett, Phillip M. Jardine and Scott C. Brooks in Soil Science Society of America Journal 66:99-108 (2002).

It has been suggested that it is possible to form a reactive barrier by adding something to the soil which will cause the uranium to become fixed. One method of doing this is to use a mineral (apatite) while a second method is to add a food substance such as acetate to the soil. This will enable bacteria to reduce the uranium (VI) to uranium (IV) which is much less soluble.

In peat like soils the uranium will tend to bind to the humic acids, this tends to fix the uranium in the soil. A report on the binding of uranium, other radioactive metals and non radioactive metal to humic acid has been published by the INE (German nuclear engineering research center) at FZK (Karlsruhe) has been published also see the paper by S. Pompe, K. Schmeide, M. Bubner, G. Geipel, K.-H. Heise, G. Bernhard and H. Nitsche in Radiochimica Acta, 2000, 88, 553-558 in which the effect of the phenol groups in the humic acid upon the binding of the uranium are studied. A series of papers have been written on coordination polymers or uranium(VI) with polycarboxylates, these have been used as models for the uranyl complexes of the humic acids.

For instance see G. Micera et al., Inorganica Chimica Acta, 1985, 109, 135-139 which is a paper about the coordination of uranium to 2,6-dihydroxybenzoate which is a carboxylic acid which has phenolic groups close to the carboxylic acid group.

2,6-dihydroxybenzoic acid

Some other work on the binding of actinides with aromatic carboxylates has been reported. A paper on the binding of neptunium(V) {neptunyl} with benzene-1,2,4,5-tetracarboxylic acid has been reported by F. Nectoux et al., Journal of the Less-Common Metals, 1984, 97, 1-10.

Benzene-1,2,4,5-tetracarboxylic acid

A PhD thesis on the interactions of uranium with Boom Clay has been published.

It is interesting to note that A. Rossberg, L. Baraniak, T. Reich, C. Hennig, G. Bernhard and H. Nitsche, Radiochimica Acta, 2000, 88, 593-597 describes an EXAFS study of the interactions of uranium with the degradation products of wood such as protocatechuic acid (3,4-dihydroxy-benzoic acid), catechol (2-hydroxyphenol), pyrogallol (1,2,3-trihydroxybenzol), and vanillic acid (4-hydroxy-3-methoxybenzoic acid).

Health effects

Soluble uranium salts are toxic, though less so than those of other heavy metals such as lead or mercury. The organ which is most affected is the kidney. Soluble uranium salts are readily excreted in the urine, although some accumulation in the kidneys does occur in the case of chronic exposure. The World Health Organization has established a daily "tolerated intake" of soluble uranium salts for the general public of 0.5 μg/kg body weight (or 35 μg for a 70 kg adult): exposure at this level is not thought to lead to any significant kidney damage.

The antidote for uranium in humans in bicarbonate, this is used because uranium(VI) forms complexes with carbonate. An alternative is to use Tiron (O. Braun, C. Contino, M.-H. Hengè, E. Ansoborlo and B. Pucci, Analusis, 1999, 27, 65-68). An article on the design of new actinide antidotes can be read at Chemical Reviews, 2003, 103, 4207-4282.

Tiron which is a phenoloic aromatic disulfonic acid which is an alternative to bicarbonate which has already been tested in animals

Humans

Studies have shown that the use of DU ammunition has no measurable detrimental health effects, either in the short or long term. The International Atomic Energy Agency reported in 2003 that, "based on credible scientific evidence, there is no proven link between DU exposure and increases in human cancers or other significant health or environmental impacts".

Gulf War syndrome

A two year study headed by Al Marshall of Sandia National Laboratories analyzed some health effects associated with accidental exposure to depleted uranium during the 1991 Gulf War, but did not consider any nonradiological reproductive toxicity, developmental toxicity, or immunological effects. Marshall’s study concluded that the reports of serious health risks from DU exposure are not supported by veteran medical statistics and were consistent with earlier studies form Los Alamos and the New England Journal of Medicine.

In the Balkans war zone, an absence of problems is seen by some as evidence of DU muntions' safety: "Independent investigations by the World Health Organization, European Commission, European Parliament, United Nations Environment Programme, United Kingdom Royal Society, and the Health Council of the Netherlands all discounted any association between depleted uranium and leukemia or other medical problems".

However in 2004, the UK Pensions Appeal Tribunal Service granted a single disability claim to a Gulf War soldier who attributed his aching joints and children's health problems to depleted uranium. This claim was vigorously disputed by the MoD.

Some studies have indicated that DU passes into humans more easily than previously thought after battlefield use.

Birth defects

Most scientific studies have found no link between uranium and birth defects, but some claim statistical correlations between soldiers exposed to DU, and those who were not, concerning reproductive abnormalities.

One study concluded that epidemiological evidence is consistent with an increased risk of birth defects in the offspring of persons exposed to DU. Environmental groups and others have expressed concern about the health effects of depleted uranium, and there is some debate over the matter. Some people have raised concerns about the use of this material, particularly in munitions, because of its mutagenicity, teratogenicity in mice, and neurotoxicity and its suspected carcinogenic potential. Additional concerns address unexploded DU munitions leeching into groundwater over time.

Several sources have attributed the increase in the rate of birth defects in the children of Gulf War veterans and in Iraqis to depleted uranium inhalation exposure, A 2001 study of 15,000 February 1991 U.S. Gulf War combat veterans and 15,000 control veterans found that the Gulf War veterans were 1.8 (fathers) to 2.8 (mothers) times more likely to have children with birth defects. In a study of UK troops, "Overall, the risk of any malformation among pregnancies reported by men was 50% higher in Gulf War Veterans (GWV) compared with Non-GWVs". The conclusion of the study stated " We found no evidence for a link between paternal deployment to the Gulf war and increased risk of stillbirth, chromosomal malformations, or congenital syndromes. Associations were found between fathers' service in the Gulf war and increased risk of miscarriage and less well-defined malformations, but these findings need to be interpreted with caution as such outcomes are susceptible to recall bias. The finding of a possible relationship with renal anomalies requires further investigation. There was no evidence of an association between risk of miscarriage and mothers' service in the gulf".

However, as yet, all evidence surrounding DU and birth defects by credible scientific sources has been deemed circumstantial. There is as yet no concrete evidence to suggest that direct exposure to DU is unsafe unless inhaled or ingested.

Animals

It has been reported that uranium has caused reproductive effects, and other health problems in rodents, frogs and other animals.

Uranium was shown to have cytotoxic, genotoxic and carcinogenic effects in animal studies (PMID 7694141, PMID 16283518). It has been shown in rodents and frogs that water soluble forms of uranium are teratogenic (PMID 16124873, PMID 11738513, PMID 12539863)

Bacterial biochemistry

It has been shown in some recent work at Manchester that bacteria can reduce and fix uranium in soils. These bacterium change soluble U(VI) into the highly insoluble complex forming U(IV) ion, hence stopping chemical leaching.

Radioactive Contamination: Radiation Poisoning

Radiation poisoning, also called "radiation sickness" or a "creeping dose", is a form of damage to organ tissue due to excessive exposure to ionizing radiation. The term is generally used to refer to acute problems caused by a large dosage of radiation in a short period, though this also has occurred with long term exposure. The clinical name for "radiation sickness" is acute radiation syndrome (ARS) as described by the CDC. A chronic radiation syndrome does exist but is very uncommon; this has been observed among workers in early radium source production sites and in the early days of the Soviet nuclear program. A short exposure can result in acute radiation syndrome; chronic radiation syndrome requires a prolonged high level of exposure.

The use of radionuclides in science and industry is strictly regulated in most countries (in the U.S. by the Nuclear Regulatory Commission). In the event of an accidental or deliberate release of radioactive material, either evacuation or sheltering in place will be the recommended measures.

Measuring radiation dosage

The rad is a unit of absorbed radiation dose defined in terms of the energy actually deposited in the tissue. One rad is an absorbed dose of 0.01 joules of energy per kilogram of tissue. The more recent SI unit is the gray (Gy), which is defined as 1 joule of deposited energy per kilogram of tissue. Thus one gray is equal to 100 rad.

To accurately assess the risk of radiation, the absorbed dose energy in rad is multiplied by the relative biological effectiveness (RBE) of the radiation to get the biological dose equivalent in rems. Rem stands for "Röntgen equivalent in man." In SI units, the absorbed dose energy in grays is multiplied by the same RBE to get a biological dose equivalent in sieverts (Sv). The sievert is equal to 100 rem.

The RBE is a "quality factor," often denoted by the letter Q, which assesses the damage to tissue caused by a particular type and energy of radiation. For alpha particles Q may be as high as 20, so that one rad of alpha radiation is equivalent to 20 rem. The Q of neutron radiation depends on their energy. However, for beta particles, x-rays, and gamma rays, Q is taken as one, so that the rad and rem are equivalent for those radiation sources, as are the gray and sievert. See the sievert article for a more complete list of Q values.

Acute (short-term) vs chronic (long-term) effects

Radiation sickness is generally associated with acute exposure and has a characteristic set of symptoms that appear in an orderly fashion. The symptoms of radiation sickness become more serious (and the chance of survival decreases) as the dosage of radiation increases. These effects are described as the deterministic effects of radiation.

Longer term exposure to radiation, at doses less than that which produces serious radiation sickness, can induce cancer as cell-cycle genes are mutated. If a cancer is radiation-induced, then the disease, the speed at which the condition advances, the prognosis, the degree of pain, and every other feature of the disease are not functions of the radiation dose to which the sufferer is exposed.

Since tumors grow by abnormally rapid cell division, the ability of radiation to disturb cell division is also used to treat cancer, and low levels of ionizing radiation have been claimed to lower one's risk of cancer.

Exposure

External vs internal exposure

External

External exposure is exposure which occurs when the radioactive source (or other radiation source) is outside (and remains outside) the organism which is exposed. Below are a series of three examples of external exposure.

• A person who places a sealed radioactive source in their pocket
• A space traveller who is irradiated by cosmic rays
• A person who is treated for cancer by either teletherapy or brachytherapy. While in brachytherapy the source is inside the person it is still external exposure because the active part of the source never comes into direct contact with the biological tissues of the person.

One of the key points is that external exposure is often relatively easy to estimate, and the irradiated objects do not become radioactive (except for a case where the radiation is an intense neutron beam which causes activation of the object). It is possible for an object to be contaminated on the outer surfaces, assuming that no radioactivity enters the object it is still a case of external exposure and it is normally the case that decontamination is easy (wash the surface).

Internal

Internal exposure is when the radioactive material enters the organism, and the radioactive atoms become incorporated into the organism. Below are a series of examples of internal exposure.

• The exposure due to ⁴⁰K present within a normal person.
• The exposure to the ingestion of a soluble radioactive substance, such as ⁸⁹Sr in cow’s milk.
• A person who is being treated for cancer by means of an open source radiotherapy method where a radioisotope is used as a drug. A review of this topic was published in 1999. Because the radioactive material becomes intimately mixed with the affected object it is often difficult to decontaminate the object or person in a case where internal exposure is occurring. While some very insoluble materials such as fission products within a uranium dioxide matrix might never be able to truly become part of an organism, it is normal to consider such particles in the lungs as a form of internal contamination which results in internal exposure. The reasoning is that the particles have entered via an orifice and can not be removed with ease from what the lay person (non biologist) would regard as within the animal. It is important to note that strictly speaking the contents of the digestive tract and the air within the lungs are outside the body of a mammal.

Nuclear warfare

Nuclear warfare is more complex because a person can be irradiated by at least three processes. The first (the major cause of burns) is not caused by ionizing radiation.

• Thermal burns from infrared heat radiation.
• Beta burns from shallow ionizing radiation (this would be from fallout particles; the largest particles in local fallout would be likely to have very high activities because they would be deposited so soon after detonation and it is likely that one such particle upon the skin would be able to cause a localized burn); however, these particles are very weakly penetrating and have a short range.
• Gamma burns from highly penetrating radiation. This would likely cause deep gamma penetration within the body, which would result in uniform whole body irradiation rather than only a surface burn. In cases of whole body gamma irradiation (circa 10 Gy) due to accidents involving medical product irradiators, some of the human subjects have developed injuries to their skin between the time of irradiation and death.

In the picture on the right, the normal clothing that the woman was wearing would have been unable to attenuate the gamma radiation and it is likely that any such effect was evenly applied to her entire body. Beta burns would be likely all over the body due to contact with fallout, but thermal burns are often on one side of the body as heat radiation does not penetrate the human body. In addition, the pattern on her clothing has been burnt into the skin. This is because white fabric reflects more infra-red light than dark fabric. As a result, the skin close to dark fabric is burned more than the skin covered by white clothing.

There is also the risk of internal radiation poisoning by ingestion of fallout particles.

Nuclear reactor accidents

Radiation poisoning was a major concern after the Chernobyl reactor accident. Thirty-one people died as an immediate result.

Of the 100 million curies (4 exabecquerels) of radioactive material, the short lived radioactive isotopes such as ¹³¹I Chernobyl released were initially the most dangerous. Due to their short half-lives of 5 and 8 days they have now decayed, leaving the more long-lived ¹³⁷Cs (with a half-life of 30.07 years) and ⁹⁰Sr (with a half-life of 28.78 years) as main dangers.

Other accidents

Improper handling of radioactive and nuclear materials lead to radiation release and radiation poisoning. The most serious of these, due to improper disposal of a medical device containing a radioactive source (teletherapy), occurred in Goiânia, Brazil in 1987.

Ingestion and inhalation

When radioactive compounds enter the human body, the effects are different from those resulting from exposure to an external radiation source. Especially in the case of alpha radiation, which normally does not penetrate the skin, the exposure can be much more damaging after ingestion or inhalation. The radiation exposure is normally expressed as a committed effective dose equivalent (CEDE).

Deliberate poisoning

On November 23, 2006, Alexander Litvinenko died due to suspected deliberate poisoning with polonium-210. His is the first case of confirmed death due to such a cause, although it is also known that there have been other cases of attempted assassination such as in the cases of KGB defector Nikolay Khokhlov and journalist Yuri Shchekochikhin where radioactive thallium was used. In addition, an incident occurred in 1990 at Point Lepreau Nuclear Generating Station where several employees acquired small doses of radiation due to the contamination of water in the office watercooler with tritium contaminated heavy water.

Prevention

The best prevention for radiation sickness is to minimize the dose suffered by the human, or to reduce the dose rate.

Distance

Increasing distance from the radiation source reduces the dose due to the inverse-square law for a point source. Distance can be increased by means as simple as handling a source with forceps rather than fingers.

Time

The longer that humans are subjected to radiation the larger the dose will be. The advice in the nuclear war manual entitled "Nuclear War Survival Skills" published by Cresson Kearny in the U.S. was that if one needed to leave the shelter then this should be done as rapidly as possible to minimize exposure.

In chapter 12 he states that "Quickly putting or dumping wastes outside is not hazardous once fallout is no longer being deposited. For example, assume the shelter is in an area of heavy fallout and the dose rate outside is 400 R/hr enough to give a potentially fatal dose in about an hour to a person exposed in the open. If a person needs to be exposed for only 10 seconds to dump a bucket, in this 1/360th of an hour he will receive a dose of only about 1 R. Under war conditions, an additional 1-R dose is of little concern."

In peacetime, radiation workers are taught to work as quickly as possible when performing a task which exposes them to irradiation. For instance, the recovery of a lost radiography source should be done as quickly as possible.

Shielding

By placing a layer of a material which will absorb the radiation between the source and the human, the dose and dose rate can be reduced. For instance, in the event of a nuclear war, it would be a good idea to shelter within a building with thick stone walls (Fallout shelter). During the height of the cold war, fallout shelters were identified in many urban areas. It is interesting to note that, under some conditions, shielding can increase the dose rate. For instance, if the electrons from a high energy beta source (such as ³²P) strike a lead surface, X-ray photons will be generated (radiation produced in this way is known as bremsstrahlung). It is best for this reason to cover any high Z materials (such as lead or tungsten) with a low Z material such as aluminium, wood, plastic. This effect can be significant if a person wearing lead-containing gloves picks up a strong beta source. Also, gamma photons can induce the emission of electrons from very dense materials by the photoelectric effect; again, by covering the high Z material with a low Z material, this potential additional source of exposure to humans can be avoided. Furthermore, gamma rays can scatter off a dense object; this enables gamma rays to "go around corners" to a small degree. Hence, to obtain a very high protection factor, the path in/out of the shielded enclosure should have several 90 degree turns rather than just one.

Reduction of incorporation into the human body

Potassium iodide (KI), administered orally immediately after exposure, may be used to protect the thyroid from ingested radioactive iodine in the event of an accident or terrorist attack at a nuclear power plant, or the detonation of a nuclear explosive. KI would not be effective against a dirty bomb unless the bomb happened to contain radioactive iodine, and even then it would only help to prevent thyroid cancer.

Fractionation of dose

While Devair Alves Ferreira received a large dose during the Goiânia accident of 7.0 Gy, he lived while his wife received a dose of 5.7 Gy and died. The most likely explanation is that his dose was fractionated into many smaller doses which were absorbed over a length of time, while his wife stayed in the house more and was subjected to continuous irradiation without a break, giving her body less time to repair some of the damage done by the radiation. In the same way, some of the people who worked in the basement of the wrecked Chernobyl plant received doses of 10 Gy, but in small fractions, so the acute effects were avoided.

It has been found in radiation biology experiments that if a group of cells are irradiated, then as the dose increases, the number of cells which survive decreases. It has also been found that if a population of cells is given a dose before being set aside (without being irradiated) for a length of time before being irradiated again, then the radiation causes less cell death. The human body contains many types of cells and the human can be killed by the loss of a single type of cells in a vital organ. For many short term radiation deaths (3 days to 30 days), the loss of cells forming blood cells (bone marrow) and the cells in the digestive system (microvilli which form part of the wall of the intestines are constantly being regenerated in a healthy human) causes death.

In the graph below, dose/survival curves for a hypothetical group of cells have been drawn, with and without a rest time for the cells to recover. Other than the recovery time partway through the irradiation, the cells would have been treated identically.

Treatment

Treatment reversing the effects of irradiation is currently not possible. Anaesthetics and antiemetics are administered to counter the symptoms of exposure, as well as antibiotics for countering secondary infections due to the resulting immune system deficiency.

There are also a number of substances used to mitigate the prolonged effects of radiation poisoning, by eliminating the remaining radioactive materials, post exposure.

Whole body vs. part of body exposure

In the case of a person who has had only part of their body irradiated then the treatment is easier, as the human body can tolerate very large exposures to the non-vital parts such as hands and feet, without having a global effect on the entire body. For instance, if the hands get a 100 Gy dose which results in the body receiving a dose (averaged over the entire body of 5 Gy) then the hands may be lost but radiation poisoning would not occur. The resulting injury would be described as localized radiation burn.

As described below, one of the primary dangers of whole-body exposure is immunodeficiency due to the destruction of bone marrow and consequent shortage of white blood cells. It is treated by maintaining a sterile environment, bone marrow transplants, and blood transfusions.

Chelation therapy can be useful to an extent if radiation poisoning is caused by the presence of heavy fissionable materials (e.g. radium or plutonium) in the bloodstream.

Experimental treatments designed to mitigate the effect on bone marrow

Neumune, an androstenediol, was introduced as a radiation countermeasure by the US Armed Forces Radiobiology Research Institute, and was under joint development with Hollis-Eden Pharmaceuticals until March, 2007. Neumune is in Investigational New Drug (IND) status and Phase I trials have been performed.

Some work has been published in which Cordyceps sinensis, a Chinese Herbal Medicine has been used to protect the bone marrow and digestive systems of mice from whole body irradation.

Table of exposure levels and symptoms

Dose-equivalents are presently stated in sieverts (Sv):

0.05–0.2 Sv (5–20 REM)

No symptoms. Potential for cancer and mutation of genetic material, according to the LNT model: this is disputed (Note: see hormesis). A few researchers contend that low dose radiation may be beneficial. 50 mSv is the yearly federal limit for radiation workers in the United States. In the UK the yearly limit for a classified radiation worker is 20 mSv. In Canada and Brazil, the single-year maximum is 50 mSv, but the maximum 5-year dose is only 100 mSv. Company limits are usually stricter so as not to violate federal limits.

0.2–0.5 Sv (20–50 REM)

No noticeable symptoms. White blood cell count decreases temporarily.

0.5–1 Sv (50–100 REM)

Mild radiation sickness with headache and increased risk of infection due to disruption of immunity cells. Temporary male sterility is possible.

1–2 Sv (100–200 REM)

Light radiation poisoning, 10% fatality after 30 days (LD 10/30). Typical symptoms include mild to moderate nausea (50% probability at 2 Sv), with occasional vomiting, beginning 3 to 6 hours after irradiation and lasting for up to one day. This is followed by a 10 to 14 day latent phase, after which light symptoms like general illness and fatigue appear (50% probability at 2 Sv). The immune system is depressed, with convalescence extended and increased risk of infection. Temporary male sterility is common. Spontaneous abortion or stillbirth will occur in pregnant women.

2–3 Sv (200–300 REM)

Moderate radiation poisoning, 35% fatality after 30 days (LD 35/30). Nausea is common (100% at 3 Sv), with 50% risk of vomiting at 2.8 Sv. Symptoms onset at 1 to 6 hours after irradiation and last for 1 to 2 days. After that, there is a 7 to 14 day latent phase, after which the following symptoms appear: loss of hair all over the body (50% probability at 3 Sv), fatigue and general illness. There is a massive loss of leukocytes (white blood cells), greatly increasing the risk of infection. Permanent female sterility is possible. Convalescence takes one to several months.

3–4 Sv (300–400 REM)

Severe radiation poisoning, 50% fatality after 30 days (LD 50/30). Other symptoms are similar to the 2–3 Sv dose, with uncontrollable bleeding in the mouth, under the skin and in the kidneys (50% probability at 4 Sv) after the latent phase.

4–6 Sv (400–600 REM)

Acute radiation poisoning, 60% fatality after 30 days (LD 60/30). Fatality increases from 60% at 4.5 Sv to 90% at 6 Sv (unless there is intense medical care). Symptoms start half an hour to two hours after irradiation and last for up to 2 days. After that, there is a 7 to 14 day latent phase, after which generally the same symptoms appear as with 3-4 Sv irradiation, with increased intensity. Female sterility is common at this point. Convalescence takes several months to a year. The primary causes of death (in general 2 to 12 weeks after irradiation) are infections and internal bleeding.

6–10 Sv (600–1,000 REM)

Acute radiation poisoning, near 100% fatality after 14 days (LD 100/14). Survival depends on intense medical care. Bone marrow is nearly or completely destroyed, so a bone marrow transplant is required. Gastric and intestinal tissue are severely damaged. Symptoms start 15 to 30 minutes after irradiation and last for up to 2 days. Subsequently, there is a 5 to 10 day latent phase, after which the person dies of infection or internal bleeding. Recovery would take several years and probably would never be complete.

Devair Alves Ferreira received a dose of approximately 7.0 Sv (700 REM) during the Goiânia accident and survived, partially due to his fractionated exposure.

10–50 Sv (1,000–5,000 REM)

Acute radiation poisoning, 100% fatality after 7 days (LD 100/7). An exposure this high leads to spontaneous symptoms after 5 to 30 minutes. After powerful fatigue and immediate nausea caused by direct activation of chemical receptors in the brain by the irradiation, there is a period of several days of comparative well-being, called the latent (or "walking ghost") phase. After that, cell death in the gastric and intestinal tissue, causing massive diarrhea, intestinal bleeding and loss of water, leads to water-electrolyte imbalance. Death sets in with delirium and coma due to breakdown of circulation. Death is currently inevitable; the only treatment that can be offered is pain therapy.

Louis Slotin was exposed to approximately 21 Sv in a criticality accident on 21 May 1946, and died nine days later on 30 May.

More than 50 Sv (>5,000 REM)

A worker receiving 100 Sv (10,000 REM) in an accident at Wood River, Rhode Island, USA on 24 July 1964 survived for 49 hours after exposure, and an operator named Cecil Kelley who received between 60 and 180 Sv (18,000 REM) to his upper body in an accident at Los Alamos, New Mexico, USA on 30 December 1958 survived for 36 hours; details of this accident can be found in the journal "Los Alamos Science", Number 23 (1995).

Cutaneous radiation syndrome

The concept of cutaneous radiation syndrome (CRS) was introduced in recent years to describe the complex pathological syndrome that results from acute radiation exposure to the skin.

Acute radiation syndrome (ARS) usually will be accompanied by some skin damage. It is also possible to receive a damaging dose to the skin without symptoms of ARS, especially with acute exposures to beta radiation or X-rays. Sometimes this occurs when radioactive materials contaminate skin or clothes.

When the basal cell layer of the skin is damaged by radiation, inflammation, erythema, and dry or moist desquamation can occur. Also, hair follicles may be damaged, causing hair loss. Within a few hours after irradiation, a transient and inconsistent erythema (associated with itching) can occur. Then, a latent phase may occur and last from a few days up to several weeks, when intense reddening, blistering, and ulceration of the irradiated site are visible. In most cases, healing occurs by regenerative means; however, very large skin doses can cause permanent hair loss, damaged sebaceous and sweat glands, atrophy, fibrosis, decreased or increased skin pigmentation, and ulceration or necrosis of the exposed tissue.

History

What may be the earliest confirmed cases of acute radiation poisoning occurred in 1879 in Barry County, Missouri, USA, where three men were fatally poisoned and a fourth permanently injured under mysterious circumstances. After chasing an animal they were hunting to the mouth of a cave, they discovered what the cave appeared to be several large veins of silver. They returned the next day to begin prospecting, but fled when they began to fall ill; by the time they had left, one of them was so ill that he was paralyzed and had to be carried to aid. In 1912, after the discovery of radium was announced, a local entrepreneur who had recalled the story investigated the cave to find that the metal was in fact radium, the first isolated veins of the metal ever found (previously, radium was only known from samples extracted from uranium-bearing pitchblende ore). The mine would be the first in the world to be excavated specifically for radium.

Although radiation was discovered in late 19th century, the dangers of radioactivity and of radiation were not immediately recognized. Acute effects of radiation were first observed in the use of X-rays when the Serbo-Croatian-American electric engineer Nikola Tesla intentionally subjected his fingers to X-rays in 1896. He published his observations concerning the burns that developed, though he attributed them to ozone rather than to X-rays. His injuries healed later.

The genetic effects of radiation, including the effects on cancer risk, were recognized much later. In 1927 Hermann Joseph Muller published research showing genetic effects, and in 1946 was awarded the Nobel prize for his findings.

Before the biological effects of radiation were known, many physicians and corporations had begun marketing radioactive substances as patent medicine and radioactive quackery. Examples were radium enema treatments, and radium-containing waters to be drunk as tonics. Marie Curie spoke out against this sort of treatment, warning that the effects of radiation on the human body were not well understood. (Curie later died from aplastic anemia assumed due to her work with radium, but later examination of her bones showed that she had been a careful laboratory worker and had a low burden of radium. A more likely cause was her exposure to unshielded X-ray tubes while a volunteer medical worker in WWI.) Eben Byers, a famous American socialite, died in 1932 after consuming large quantities of radium over several years; his death drew public attention to dangers of radiation. By the 1930s, after a number of cases of bone necrosis and death in enthusiasts, radium-containing medical products had nearly vanished from the market.

Nevertheless, dangers of radiation weren't fully appreciated by scientists until later. In 1945 and 1946, two U.S. scientists died from acute radiation exposure in separate criticality accidents. In both cases, victims were working with large quantities of fissile materials without any shielding or protection.

Atomic bombings of Hiroshima and Nagasaki resulted in a large number of incidents of radiation poisoning, allowing for greater insight into its symptoms and dangers.

Radioactive Contamination: Plutonium in the Environment

Plutonium in the environment is an article which is part of the actinides in the environment series. Almost all plutonium present in the environment is due to human activity because the majority of plutonium isotopes are shortlived on a geological timescale. It has been argued that some natural plutonium (the very long lived ²⁴⁴Pu isotope) can be found in nature. This isotope has been found in lunar soil, meteorites, and in the Oklo natural reactor. But in general it is normally considered that the bulk of all plutonium is man made. According to one paper on marine sediments for plutonium in marine sediments, bomb fall out is responsible for the majority of the ²³⁹Pu and ²⁴⁰Pu (66% and 59% respectively of that found in the English Channel) while nuclear reprocessing is responsible for the majority of the ²³⁸Pu and ²⁴¹Pu present in the sea (bomb tests are only responsible for 6.5 and 16.5% of these isotopes respectively).

Bomb detonations

About 3.5 tons of plutonium have been released into the environment by atomic bomb tests. While this might sound like a large amount it has only resulted in a very small dose to the majority of the humans on the earth. Overall the health effects of the fission products are far greater than the effects of the actinides released by a nuclear bomb detonation. The plutonium from the Pu fuel of the bomb is converted into a high fired oxide which is carried high into the air. It slowly falls to earth as global fallout and is not soluble, hence as a result it is difficult for this plutonium to be incorporated into an animal if taken by mouth. Much of this plutonium will become tightly absorbed onto sediments of lakes, rivers and oceans. However, about 66% of the plutonium from a bomb explosion is formed by the neutron capture of uranium-238; this plutonium is not converted by the bomb into a high fired oxide as it is formed more slowly. As a result this formed plutonium is more soluble and more able to cause harm when it falls to earth.

Some of the plutonium can be deposited close to the point of detonation. The glassy trinitite formed by the first atom bomb has been examined to determine what actinides and other radioisotopes it contained. A recent paper reports the levels of long lived radioisotopes in the trinitite. The trinitite was formed from feldspar and quartz which were melted by the heat. Two samples of trinitite were used, the first (left hand side bars) was taken from between 40 and 65 meters of ground zero while the other sample was taken from further away from the ground zero point.

Levels of radioactivity in the trinitite glass from two different samples as measured by gamma spectroscopy on lumps of the glass. The americium content is the current content while all the other isotopes have been back calculated to shortly after the moment of detonation.

The ¹⁵²Eu and ¹⁵⁴Eu was mainly formed by the neutron activation of the europium in the soil, it is clear that the level of radioactivity for these isotopes is highest where the neutron dose to the soil was larger. Some of the ⁶⁰Co is generated by activation of the cobalt in the soil, but some was also generated by the activation of the cobalt in the steel (100 foot) tower. This ⁶⁰Co from the tower would have been scattered over the site reducing the difference in the soil levels.

The ¹³³Ba and ²⁴¹Am are due to the neutron activation of barium and plutonium inside the bomb. The barium was present in the form of the nitrate in the chemical explosives used while the plutonium was the fissile fuel used.

It is interesting to note that the ¹³⁷Cs level is higher in the sample which was further away from the ground zero point. This is thought to be because the precursors to the ¹³⁷Cs (¹³⁷I and ¹³⁷Xe) and the caesium to a lesser degree are volatile. The natural radioisotopes in the glass are about the same in both locations.

In this paper a sample of the glass was digested and the plutonium extracted from it, and the mass ratio of the isotopes was calculated from the radiometric measurements. In light green the isotopic signature for the plutonium used for making the bomb is shown, and on the right in dark green the signature of the plutonium in the trinitite glass is shown. It is very clear that ²³⁸Pu and ²⁴¹Pu were generated during the detonation, so it is reasonable to conclude that some ²⁴⁰Pu was formed during the detonation.

Isotropic signatures of the plutonium before and after the detonation.

As the ²³⁹Pu/²⁴⁰Pu ratio only changed slightly during the detonation, it has been commented that this isotope ratio for the majority of atom bombs (In Japan the ²³⁹Pu/²⁴⁰Pu ratio in soil is normally in the range 0.17 to 0.19) is very different than from the bomb dropped upon Nagasaki, so the forest soil and the lake sediment layer containing the local fallout from World War II bomb is very different from the layers due to global fallout from bomb tests conducted later.

Bomb safety trials

One form of release of plutonium into the environment has been safety trials in these experiments nuclear bombs have been subjected to simulated accidents or have been detonated with an abnormal initiation of the chemical explosives. An abnormal implosion will result in a compression of the pit which is less uniform and smaller than the designed compression in the device. Such an abnormal implosion could result from an accident which triggers one or more of the detonators which trigger the chemical explosive charges.

As a result of these experiments (where no or very little nuclear fission occurs) plutonium metal has been scattered around near the site of the experiment. While some of these tests have been done inside holes in the ground, other such tests were conducted in open air. A paper on the radioisotopes left on an island by the French nuclear bombs tests of the 20th century has been printed by the International Atomic Energy Agency and a section of this report deals with plutonium contamination resulting from such tests.

The two basic fission weapon designs.

Other related trials were conducted at Maralinga, South Australia here both normal bomb detonations and "safety trials" have been conducted. While the activity from the fission products has decayed away almost totally (as of 2006) the plutonium remains active. A report (warning it is very big) can be read at while a smaller report can be seen at.

Atomic batteries

Space

Diagram of an RTG used on the Cassini probe

Another potential source of plutonium being introduced into the environment is the reentry of artificial satellites containing atomic batteries. There have been several such incidents, the most prominent being the Apollo 13 mission. The Apollo Lunar Surface Experiment Package carried on the Lunar Module re-entered the atmosphere over the South Pacific. Many atomic batteries have been of the Radioisotope thermoelectric generator (RTG) type.

Chain reactions do not occur inside RTGs, so such a nuclear meltdown is impossible. In fact, some RTGs are designed so that fission does not occur at all; rather, forms of radioactive decay which cannot trigger other radioactive decays are used instead. As a result, the fuel in an RTG is consumed much more slowly and much less power is produced.

which cannot trigger other radioactive decays are used instead. As a result, the fuel in an RTG is consumed much more slowly and much less power is produced.

RTGs are still a potential source of radioactive contamination: if the container holding the fuel leaks, the radioactive material will contaminate the environment. The main concern is that if an accident were to occur during launch or a subsequent passage of a spacecraft close to Earth, harmful material could be released into the atmosphere. However, this event is extremely unlikely with current RTG cask designs.

In order to minimise the risk of the radioactive material being released, the fuel is typically stored in individual modular units with their own heat shielding. They are surrounded by a layer of iridium metal and encased in high-strength graphite blocks. These two materials are corrosion and heat-resistant. Surrounding the graphite blocks is an aeroshell, designed to protect the entire assembly against the heat of reentering the earth's atmosphere. The plutonium fuel is also stored in a ceramic form that is heat-resistant, minimising the risk of vaporization and aerosolization. The ceramic is also highly insoluble.

The US Department of Energy has conducted seawater tests and determined that the graphite casing, which was designed to withstand reentry, is stable and no release of plutonium should occur. Subsequent investigations have found no increase in the natural background radiation in the area. The Apollo 13 accident represents an extreme scenario due to the high re-entry velocities of the craft returning from cislunar space. This accident has served to validate the design of later-generation RTGs as highly safe.

The Plutonium-238 used in RTGs has a half-life of 88 years, as opposed to the plutonium-239 used in nuclear weapons and reactors, which has a half-life of 24,100 years.

Pacemakers

Some heart pacemakers which are powered by RTGs using 238Pu have been made.

Nuclear fuel cycle

Plutonium has been released into the environment in aqueous solution from nuclear reprocessing and uranium enrichment plants. The chemistry of this plutonium is different from that of the metal oxides formed from nuclear bomb detonations.

One example of a site (military not civil) where plutonium entered the soil is Rocky Flats where in the recent past XANES (a X-ray spectrscopy) has been used to determine the chemical nature of the plutonium in the soil. The XANES was used to determine the oxidation state of the plutonium, while EXAFS was used to investigate the structure of the plutonium compound present in the soil and concrete.

The XANES experiments done on plutonium in soil, concrete and standards of the different oxidation states.

Chernobyl

Because plutonium oxide is very involatile, most of the plutonium in the reactor was not released during the fire. However that which was released can be measured. V.I. Yoschenko et al. reported that grass and forest fires can make the caesium, strontium and plutonium become mobile in the air again. (Journal of Environmental Radioactivity, 2006, 86, 143-163.) As an experiment fires were set and the levels of the radioactivity in the air downwind of these fires was measured.

Nuclear crime

One case exists of a German man who attempted to poison his ex-wife with plutonium stolen from WAK (Wiederaufbereitungsanlage Karlsruhe). WAK was a small scale reprocessing plant where he worked. He did not steal a large amount of plutonium, just some rags used for wiping surfaces and a small amount of liquid waste. This man was sent to prison for his crime. At least two people (besides the criminal) were contaminated by the plutonium. Two flats in Rhineland-Palatinate were contaminated. These were later cleaned at a cost of two million euro.

For photographs of the case and details of other nuclear crimes see which was presented by a worker at the ITU. A general over view of the forensic matters associated with plutonium exists.

The details of how the two flats in Landau were cleaned has been recorded. In addition it has been claimed that a house in Reading, Berkshire) has been contaminated with plutonium.

Environmental chemistry

Overview

Plutonium like other actinides readily forms a dioxide plutonyl core (PuO₂). In the environment, this plutonyl core readily complexes with carbonate as well as other oxygen moieties (OH^-, NO₂^-, NO₃^-, and SO₄^-2) to form charged complexes which can be readily mobile with low affinities to soil.

• PuO₂(CO₃)₁^-2
• PuO₂(CO₃)₂^-4
• PuO₂(CO₃)₃^-6

PuO₂ formed from neutralizing highly acidic nitric acid solutions tends to form polymeric PuO₂ which is resistant to complexation. Plutonium also readily shifts valences between the +3, +4, +5 and +6 states. It is common for some fraction of plutonium in solution to exist in all of these states in equilibrium.

Binding to soil

Plutonium is known to bind to soil particles very strongly, see above for a X-ray spectroscopic study of plutonium in soil and concrete. While caesium has very different chemistry to the actinides, it is well known that both caesium and many of the actinides bind strongly to the minerals in soil. Hence it has been possible to use ¹³⁴Cs labeled soil to study the migration of Pu and Cs is soils. It has been shown that colloidal transport processes control the migration of Cs (and will control the migration of Pu) in the soil at the Waste Isolation Pilot Plant according to R.D. Whicker and S.A. Ibrahim, Journal of Environmental Radioactivity, 2006, 88, 171-188.

Microbiological chemistry

Mary Neu (at Los Alamos in the USA) has done some work which suggests that bacteria can accumilate plutonium because the iron transport systems used by the bacteria also function as plutonium transport systems.

Biology

Plutonium ingested by or injected into humans is transported in the transferrin based iron(III) transport system and then is stored in the liver in the iron store (ferritin), after an exposure to plutonium it is important to rapidly inject the subject with a chelating agent such as calcium complex of DTPA. This antidote is useful for a single one off exposure such as that which would occur if a glove box worker was to cut their hand with a Pu contaminated object. The calcium complex has faster metal binding kinetics than the zinc complex but if the calcium complex is used for a long time it tends to remove important minerals from the person. The zinc complex is less able to cause these effects.

Plutonium that is inhaled by humans lodges in the lungs and is slowly translocated to the lymph nodes. Inhaled plutonium has been shown to lead to lung cancer in experimental animals.

Radioactive Contamination: Nuclear Fallout

Fallout is the residual radiation hazard from a nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion. It commonly refers to the radioactive dust created when a nuclear weapon explodes. This radioactive dust, consisting of hot particles, is a kind of radioactive contamination. It can lead to contamination of the food chain.

Types

There are many types of fallout, ranging from the global type to the more area-restricted types of fallout.

Worldwide

After an air burst, the fission products, unfissioned nuclear material, and weapon residues which have been vaporized by the heat of the fireball will condense into a fine suspension of very small particles 10 nm to 20 µm in diameter. These particles may be quickly drawn up into the stratosphere, particularly if the explosive yield exceeds 10 kt.

Initially little was known about the dispersion of nuclear fallout on a global scale. The AEC assumed that fallout would be dispersed evenly across the globe, dispersed by atmospheric winds and will gradually settle to the Earth's surface after weeks, months, and even years as worldwide fallout. Nuclear products were deposited in the Northern Hemisphere becoming "far more dangerous than they had originally been estimated".

The radio-biological hazard of worldwide fallout is essentially a long-term one because of the potential accumulation of long-lived radioisotopes (such as strontium-90 and caesium-137) in the body as a result of ingestion of foods containing the radioactive materials. This hazard is much less serious than those which are associated with local fallout, which is of much greater immediate operational concern.

Local

In a land or water surface burst, large amounts of earth or water will be vaporized by the heat of the fireball and drawn up into the radioactive cloud. This material will become radioactive when it condenses with fission products and other radiocontaminants that have become neutron-activated. Many of the isotopes in the table below will decay into the isotopes that many people are more familiar with.

Isotope	Refractory index
91Sr	0.2
92Sr	1.0
95Zr	1.0
99Mo	1.0
106Ru	0.0
131Sb	0.1
132Te	0.0
134Te	0.0
137Cs	0.0
140Ba	0.3
141La	0.7
144Ce	1.0

There will be large amounts of particles of less than 100 nm to several millimeters in diameter generated in a surface burst in addition to the very fine particles which contribute to worldwide fallout. The larger particles spill out of the stem and cascade down the outside of the fireball in a downdraft even while the cloud rises, so fallout begins to arrive near ground zero within an hour, and more than half the total bomb debris is deposited on the ground within about 24 hours as local fallout.

The chemical properties of the different elements in the fallout will control the rate at which they are deposited on the ground. The less volatile elements will deposit first.

Severe local fallout contamination can extend far beyond the blast and thermal effects, particularly in the case of high yield surface detonations. The ground track of fallout from an explosion depends on the weather situation from the time of detonation onwards. In stronger winds, fallout travels faster but takes the same time to descend, so although it covers a larger path, it is more spread out or diluted. So the width of the fallout pattern for any given dose rate is reduced where the downwind distance is increased by higher winds. The total amount of activity deposited up to any given time is the same irrespective of the wind pattern, so the overall casualty figures from fallout will generally be independent of the winds. But thunderstorms can bring down activity as rain more rapidly than dry fallout, particularly if the mushroom cloud is low enough to be below, or mixed with, the thunderstorm.

Whenever individuals remain in a radiologically contaminated area, such contamination will lead to an immediate external radiation exposure as well as a possible later internal hazard from inhalation and ingestion of radiocontaminants, such as the rather short-lived iodine-131, which is accumulated in the thyroid.

Factors affecting fallout

Location

There are two main considerations for the location of an explosion: height and surface composition. A nuclear weapon detonated in the air, called an air burst, will produce less fallout than a comparable explosion near the ground. Less particulate matter will be contaminated by an air burst. Detonations at the surface (surface bursts) will tend to produce more fallout material.

In case of water surface bursts, the particles tend to be rather lighter and smaller, producing less local fallout but extending over a greater area. The particles contain mostly sea salts with some water; these can have a cloud seeding effect causing local rainout and areas of high local fallout. Fallout from a seawater burst is difficult to remove once it has soaked into porous surfaces because the fission products are present as metallic ions which become chemically bonded to many surfaces. Water and detergent washing is effective on removing less than about 50% of this chemically bonded activity from concrete or steel (complete decontamination requires aggressive treatment like sandblasting, or acidic treatment). After the Crossroads underwater test, it was found that wet fallout needs to be immediately removed from ships by continuous water washdown (such as from the fire sprinkler system on the decks).

For subsurface bursts, there is an additional phenomenon present called "base surge". The base surge is a cloud that rolls outward from the bottom of the subsiding column, which is cause by an excessive density of dust or water droplets in the air. For underwater bursts, the visible surge is, in effect, a cloud of liquid (usually water) droplets with the property of flowing almost as if it were a homogeneous fluid. After the water evaporates, an invisible base surge of small radioactive particles may persist.

For subsurface land bursts, the surge is made up of small solid particles, but it still behaves like a fluid. A soil earth medium favors base surge formation in an underground burst. Although the base surge typically contains only about 10% of the total bomb debris in a subsurface burst, it can create larger radiation doses than fallout near the detonation, because it arrives sooner than fallout, before much radioactive decay has occurred.

Meteorological

Meteorological conditions will greatly influence fallout, particularly local fallout. Atmospheric winds are able to bring fallout over large areas. For example, as a result of a Castle Bravo surface burst of a 15 Mt thermonuclear device at Bikini Atoll on March 1, 1954, a roughly cigar-shaped area of the Pacific extending over 500 km downwind and varying in width to a maximum of 100 km was severely contaminated. There are three very different versions of the fallout pattern from this test, because the fallout was only measured on a small number of widely spaced Pacific Atolls. The two alternative versions both ascribe the high radiation levels at north Rongelap to a downwind hotspot caused by the large amount of radioactivity carried on fallout particles of about 50-100 micrometres size.

After Bravo, it was discovered that fallout landing on the ocean disperses in the top water layer (above the thermocline at 100 m depth), and the land equivalent dose rate can be calculated by multiplying the ocean dose rate at two days after burst by a factor of about 530. In other 1954 tests, including Yankee and Nectar, hotspots were mapped out by ships with submersible probes, and similar hotspots occurred in 1956 tests such as Zuni and Tewa However, the major U.S. 'DELFIC' (Defence Land Fallout Interpretive Code) computer calculations use the natural size distributions of particles in soil instead of the afterwind sweep-up spectrum, and this results in more straightforward fallout patterns lacking the downwind hotspot.

Snow and rain, especially if they come from considerable heights, will accelerate local fallout. Under special meteorological conditions, such as a local rain shower that originates above the radio-active cloud, limited areas of heavy contamination just downwind of a nuclear blast may be formed.

Effects

A wide range of biological changes may follow the irradiation of animals. These vary from rapid death following high doses of penetrating whole-body radiation, to essentially normal lives for a variable period of time until the development of delayed radiation effects, in a portion of the exposed population, following low dose exposures.

The unit of actual exposure is the Röntgen which is defined in ionisations per unit volume of air, and all ionisation based instruments (including geiger counters and ionisation chambers) measure exposure. However, effects depend on the energy per unit mass, not the exposure measured in air. A deposit of 1 joule per kilogram has the unit of 1 gray. For 1 MeV energy gamma rays, an exposure of 1 röntgen in air will produce a dose of about 0.01 gray (1 centigray, cGy) in water or surface tissue. Because of shielding by the tissue surrounding the bones, the bone marrow will only receive about 0.67 cGy when the air exposure is 1 röntgen and the surface skin dose is 1 cGy. Some of the lower values reported for the amount of radiation which would kill 50% of personnel (the 'LD₅₀') refer to bone marrow dose, which is only 67% of the air dose.

Short term

When comparing the effects of various types or circumstances, the dose which is lethal to 50% of a given population is a common parameter. The term is usually defined for a specific time, which is generally limited to studies of acute lethality. The common time periods used are 30 days or less for most small laboratory animals and to 60 days for large animals and humans. The LD₅₀

figure assumes that the individuals did not receive other injuries or medical treatment.

In the 1950s, the LD₅₀ for gamma rays was set at 3.5 Gy, while under more dire conditions of war (a bad diet, little medical care, poor nursing) the LD₅₀ was 2.5 Gy (250 rad). There have been few documented cases of survival beyond 6 Gy. One person at Chernobyl survived a dose of more than 10 Gy, but many of the persons exposed there were not uniformly exposed over their entire body. If a person is exposed in a non-homogeneous manner then a given dose (averaged over the entire body) is less likely to be of a lethal dose. For instance if a person gets a hand/low arm dose of 100 Gy which gives them an overall dose of 4 Gy then they are more likely to survive than a person who gets a 4 Gy dose uniformly over their entire body. A hand dose of 10 Gy or more will likely result in loss of the hand; a British industrial radiographer who got a lifetime hand dose of 100 Gy lost his hand because of radiation dermatitis. Most people become ill after an exposure to 1 Gy or more. The fetuses of pregnant women are often more vulnerable than the host body and may miscarry, especially in the first trimester. Though the human biology resists mutation from large radiation exposure; grossly mutated fetuses usually miscarry, and this often causes gene-faults.

One hour after a surface burst, the radiation from fallout in the crater region is 30 grays per hour (Gy/h). Civilian dose rates in peacetime range from 30 to 100 µGy per year.

Fallout radiation decays exponentially relatively quickly with time. Most areas become fairly safe for travel and decontamination after three to five weeks.

For yields of up to 10 kt, prompt radiation is the dominant producer of casualties on the battlefield. Humans receiving an acute incapacitating dose (30 Gy) will have their performance degraded almost immediately and become ineffective within several hours. However, they will not die until 5 to 6 days after exposure assuming they do not receive any other injuries.

Individuals receiving less than a total of 1.5 Gy will not be incapacitated. People receiving doses greater than 1.5 Gy will become disabled; some will eventually die.

A dose of 5.3 Gy to 8.3 Gy is considered lethal but not immediately incapacitating. Personnel exposed to this amount of radiation will have their performance degraded within 2 to 3 hours, depending on how physically demanding the tasks they must perform are, and will remain in this disabled state at least 2 days. However, at that point they will experience a recovery period and be effective at performing non-demanding tasks for about 6 days, after which they will relapse for about 4 weeks. At this time they will begin exhibiting symptoms of radiation poisoning of sufficient severity to render them totally ineffective. Death follows at approximately 6 weeks after exposure, although results may vary.

Long term

Late or delayed effects of radiation occur following a wide range of doses and dose rates. Delayed effects may appear months to years after irradiation and include a wide variety of effects involving almost all tissues or organs. Some of the possible delayed consequences of radiation injury are life shortening, carcinogenesis, cataract formation, chronic radiodermatitis, decreased fertility, and genetic mutations.

Tactical military considerations

Blast injuries and thermal burns from the use of nuclear weapons for military action in many cases will far outnumber radiation injuries. However, radiation effects are considerably more complex and varied than are blast or thermal effects and are subject to considerable misunderstanding.

The closer to ground an atomic bomb is detonated, the more dust and debris is thrown into the air, resulting in greater amounts of local fallout. From a tactical standpoint, this has the disadvantage of hindering any occupation/invading efforts until the fallout clears, but more directly, the impact with the ground severely limits the destructive force of the bomb. For these reasons, ground bursts are not usually considered tactically advantageous, with the exception of hardened underground targets such as missile silos or command centers, however "salting" enemy territory with a fallout-heavy atomic burst can be used to deny ill-equipped civilians/military personnel access to a contaminated area.

Fallout protection

During the Cold War, the governments of the U.S. and USSR attempted to educate their citizens about surviving a nuclear attack. In the U.S., this effort became known as Civil Defense. The government provided procedures on minimizing short-term exposure to fallout, but currently, the popular attitude towards fallout protection is that short-term survival in a global thermonuclear war would be futile, and fallout shelters are no longer maintained.

Nuclear reactor accident

Fallout can also refer to nuclear accidents, although a nuclear reactor does not explode like a nuclear weapon. The isotopic signature of bomb fallout is very different from the fallout from a serious power reactor accident (such as Chernobyl). The key differences are in volatility and half-life.

Volatility

The boiling point of an element (or its compounds) is able to control the percentage of that element which is released by a power reactor accident. In addition the ability of an element to form a solid controls the rate at which it is deposited on the ground after it has been injected into the atmosphere by a nuclear detonation.

Half-life

In bomb fallout, a large amount of short-lived isotopes such as ⁹⁷Zr are present. This isotope and the other short-lived isotopes are being constantly generated in a power reactor, but because the criticality occurs over a long length of time the majority of these short lived isotopes decay before they can be released.

Below is shown a comparison of the calculated gamma dose rates in open air from the fallout of a fission bomb and of the Chernobyl release. It is clear that average half-life of the Chernobyl release is longer than that for the bomb fallout.

Radioactive Contamination: Fission product

Fission products are the atomic fragments left after a large nucleus fissions. Typically, a large nucleus like Uranium fissions by splitting into two smaller nuclei, along with a few neutrons and a large release of energy in the form of heat (kinetic energy of the nuclei), gamma rays and neutrinos. The two smaller nuclei are the "fission products".

Formation and decay

The sum of the atomic weight of the two atoms produced by the fission of one atom is always less than the atomic weight of the original atom. This is because some of the mass is lost as free neutrons and large amounts of energy.

Since the nuclei that can readily undergo fission are particularly neutron-rich (e.g. 61% of the nucleons in uranium-235 are neutrons), the initial fission products are almost always more neutron-rich than stable nuclei of the same mass as the fission product (e.g. stable ruthenium-100 is 56% neutrons, stable xenon-134 is 60%). The initial fission products therefore may be unstable and typically undergo beta decay towards stable nuclei, converting a neutron to a proton with each beta emission. (Fission products do not emit alpha particles.)

A few neutron-rich and short-lived initial fission products first decay by emitting a neutron. This is the source of delayed neutrons which play an important role in control of a nuclear reactor.

The first beta decays are rapid, and may release high energy beta particles or gamma radiation. However, as the fission products approach stable nuclear conditions, the last one or two decays may have a long halflife and release less energy. There are a few exceptions with relatively long halflives and high decay energy, such as:

• Sr-90 (high energy beta, halflife 30 years)
• Cs-137 (high energy gamma, halflife 30 years)
• Sn-126 (even higher energy gamma, but long halflife of 230,000 years means a slow rate of radiation release, and the yield of this nuclide per fission is very low)

Yield

Each fission of a parent atom produces a different set of fission product atoms. However, while an individual fission is not predictable, the fission products are statistically predictable. The amount of any particular isotope produced per fission is called its yield, typically expressed as % per parent fission; therefore, yields total to 200% not 100%.

While fission products include every element from zinc through the lanthanides, the majority of the fission products occurs in two peaks. One peak occurs at about (expressed by atomic number) strontium to ruthenium while the other peak is at about tellurium to neodymium. The exact yield is somewhat dependent on the parent atom, and also on the energy of the initiating neutron.

In general the higher the energy of the state that undergoes nuclear fission, the more likely that the two fission products have similar mass. Hence as the neutron energy increases and/or the energy of the fissile atom increases, the valley between the two peaks becomes more shallow. For instance, the curve of yield against mass for Pu-239 has a more shallow valley than that observed for U-235 when the neutrons are thermal neutrons. The curves for the fission of the later actinides tend to make even more shallow valleys. In extreme cases such as ²⁵⁹Fm, only one peak is seen.

The adjacent figure shows a typical fission product distribution from the fission of uranium. Note that in the calculations used to make this graph, the activation of fission products was ignored and the fission was assumed to occur in a single moment rather than a length of time. In this bar chart results are shown for different cooling times (time after fission). Because of the stability of nuclei with even numbers of protons and/or neutrons, the curve of yield against element is not a smooth curve but tends to alternate. (But note that the curve against mass number is smooth).

Characteristics

Medium-lived
fission products

Prop: Unit:	t½ a	Yield %	Q * KeV	βγ *
155Eu	4.76	.0803	252	βγ
85Kr	10.76	.2180	687	βγ
113mCd	14.1	.0008	316	β
90Sr	28.9	4.505	2826	β
137Cs	30.23	6.337	1176	βγ
121mSn	43.9	.00005	390	βγ
151Sm	90	.5314	77	β

Long-lived
fission products

Prop: Unit:	t½ Ma	Yield %	Q * KeV	βγ *
99Tc	.211	6.1385	294	β
126Sn	.230	.1084	4050	βγ
79Se	.295	.0447	151	β
93Zr	1.53	5.4575	91	βγ
135Cs	2.3	6.9110	269	β
107Pd	6.5	1.2499	33	β
129I	15.7	.8410	194	βγ

The adjacent tables provides information on the half-life, yield and decay energies for some more important fission products. A more detailed description of individual products is provided in Fission products (by element) and in Long-lived fission products, and in articles on specific radionuclides.

The following chart provides information on the electronegativity of the fission products.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

4

Ionization energy increases → Electronegativity increases →

Ga 1.81

Ge 2.01

As 2.18

Se 2.55

Br 2.96

Kr 3.00

5

Rb 0.82

Sr 0.95

Y 1.22

Zr 1.33

Nb 1.6

Mo 2.16

Tc 1.9

Ru 2.2

Rh 2.28

Pd 2.20

Ag 1.93

Cd 1.69

In 1.78

Sn 1.96

Sb 2.05

Te 2.1

I 2.66

Xe 2.67

6

Cs 0.79

Ba 0.89

La 1.1

Ce 1.12

Pr 1.13

Nd 1.14

Pm 1.13

Sm 1.17

Eu 1.2

Gd 1.2

Tb 1.1

Dy 1.22

Lanthanides act like Group 3

Ac 1.1

Th 1.3

Pa 1.5

U 1.38

Np 1.36

Pu 1.28

Am 1.13

Cm 1.28

Bk 1.3

Cf 1.3

Not all Actinides act like Group 3

Fission product production

Small amounts of fission products are naturally formed as the result of either spontaneous fission of natural uranium, which occurs at a low rate, or as a result of neutrons from radioactive decay or reactions with cosmic ray particles. The microscopic tracks left by these fission products in some natural minerals can be used to provide a method of dating old materials.

About 1.5 billion years ago, in a uranium ore body in Africa, a natural nuclear fission reactor operated for a few hundred thousand years and produced approximately 5 tonnes of fission products. These fission products were important in providing proof that the natural reactor had occurred. More details are provided in the linked article.

Fission products are produced in nuclear weapons, with the amount depending on the type of weapon.

The largest source of fission products is from nuclear reactors. In current nuclear power reactors, a small percentage of the uranium in the fuel is converted into fission products as an unavoidable by-product of energy generation. Most of these fission products remain in the fuel unless there is fuel failure, or an accident, or the fuel is reprocessed.

Applications

Supply of radioactive isotopes

Some fission products (such as Cs-137) are used in medical and industrial radioactive sources.

Nuclear reactor control

Some fission products decay with the release of a neutron. Since there may be a short delay in time between the original fission event (which release its own "prompt" neutrons immediately) and the release of these neutrons, the latter are termed "delayed neutrons". These delayed neutrons are important to nuclear reactor control.

Nuclear reactor poisons

Some of the fission products have a high neutron absorption capacity, such as xenon-135 and samarium-149. Since a nuclear reactor depends on a balance in the neutron production and absorption rates, these fission product remove neutrons from the reactor and will tend to shut the reactor down or "poison" the reactor. Nuclear fuels and reactors are designed to address this phenomena through such features as burnable poisons and control rods. More details are provided in the article on nuclear reactor poisons.

Fission Product Decay with time

For fission of Uranium-235 the most common radioactive fission products include isotopes of iodine, caesium, strontium, xenon and barium. It is important to understand that the size of the threat becomes smaller with the passage of time, locations where radiation fields which posed immediate mortal threats (such as much of the Chernobyl power plant on day one of the accident and the ground zero sites of Japanese atomic bombings [6 hours after detonation]) are now safe as the radioactivity has decayed away. Please for instance see the graph below of the gamma dose rate due to Chernobyl fallout as a function of time after the accident. Many of the fission products decay through very shortlived isotopes to form stable isotopes, but also a considerable number of the radioisotopes have half lives longer than a day.

The radioactivity in the fission product mixture is mostly short lived isotopes such as I-131 and ¹⁴⁰Ba, after about four months ¹⁴¹Ce, ⁹⁵Zr/⁹⁵Nb and ⁸⁹Sr take the largest share, while after about two or three years the largest share is taken by ¹⁴⁴Ce/144Pr, ¹⁰⁶Ru/¹⁰⁶Rh and ¹⁴⁷Pm. Later ⁹⁰Sr and ¹³⁷Cs are the main radioisotopes, being succeeded by ⁹⁹Tc. Note that in the case a release of radioactivity from a power reactor or used fuel that only some elements are released, as a result the isotopic signature of the radioactivity is very different from an open air nuclear detonation where all the fission products are dispersed.

Fission products in power reactors

In a nuclear power reactor, the main types of radioactivity are fission products, actinides and activation products. Fission products are the largest amount of radioactivity for the first several hundred years, while actinides are dominant roughly 10³ to 10⁵ years after fuel use.

Fission occurs in the nuclear fuel, and the fission products are primarily retained within the fuel close to where they are produced. These fission products are important to the operation of the reactor because (as noted above) some fission products contribute delayed neutrons that are useful for reactor control while others are neutron poisons that tend to inhibit the nuclear reaction. The buildup of the fission product poisons is a key factor in determining the maximum duration a given fuel element can be kept within the reactor. The decay of short-lived fission products also provide a source of heat within the fuel that continues even after the reactor has been shutdown and the fission reactions stopped. It is this decay heat that sets the requirements for cooling of a reactor after shutdown. More details on these topics are provided in the articles on nuclear power plants and used nuclear fuel.

If the fuel cladding around the fuel develops holes, then fission products can leak into the primary coolant. Depending on the fission product chemistry, it may settle within the reactor core or travel through the coolant system. Coolant systems include chemistry control systems that among other purposes, will tend to remove such fission products. In a well-designed power reactor running under normal conditions, the radioactivity of the coolant is very low.

Fission products in nuclear weapons

Nuclear weapons use fission as either the partial or the main energy source. Depending on the weapon design and where it is exploded, the relative importance of the fission product radioactivity will vary compared to the activation product radioactivity in the total fallout radioactivity.

The immediate fission products from nuclear weapon fission are essentially the same as those from any other fission source, depending slightly on the particular nuclide that is fissioning. However, the very short time scale for the reaction makes a difference in the particular mix of isotopes produced from an atomic bomb.

For example, the ¹³⁴Cs/¹³⁷Cs ratio provides an easy method of distinguishing between fallout from a bomb and the fission products from a power reactor. Almost no Cs-134 is formed by nuclear fission (because xenon-134 is stable). The ¹³⁴Cs is formed by the neutron activation of the stable ¹³³Cs which is formed by the decay of isotopes in the isobar (A = 133). so in a momentary criticality by the time that the neutron flux becomes zero too little time will have passed for any ¹³³Cs to be present. While in a power reactor plenty of time exists for the decay of the isotopes in the isobar to form ¹³³Cs, the ¹³³Cs thus formed can then be activated to form ¹³⁴Cs only if the time between the start and the end of the criticality is long.

According to Jiri Hala's textbook the radioactivity in the fission product mixture (due to an atom bomb) is mostly caused by short-lived isotopes such as I-131 and Ba-140. After about four months Ce-141, Zr-95/Nb-95, and Sr-89 represent the largest share of radioactive material. After two to three years, Ce-144/Pr-144, Ru-106/Rh-106, and Promethium-147 are the bulk of the radioactivity. After a few years, the radiation is dominated by Strontium-90 and Caesium-137, whereas in the period between 10,000 and a million years it is Technetium-99 that dominates.

Countermeasures against the worst fission products found in accident fallout

The purpose of radiological emergency preparedness is to protect people from the effects of radiation exposure after an accident at a nuclear power plant. Evacuation is the most effective protective measure in the event of a radiological emergency because it protects the whole body (including the thyroid gland and other organs) from all radionuclides and all exposure pathways. However, in situations where evacuation is impossible, calling for in-place sheltering, there are measures which lend some degree of protection against harmful radioisotopes

The mixture of radioactive fission products found in the fallout from a nuclear bomb are very different in nature to those found in spent power reactor fuel. This is because the reactor fuel will have had more time for the short lived isotopes to decay, and because for many accident types that the volatile elements are liberated while the involitiles are retained at the accident site. As a result the contribution of many shortlived (eg ⁹⁷Zr) and/or involtiles to the off site gamma dose is less for accident fallout than it is for local fallout from a bomb detonation.

Iodine

At least three isotopes of iodine are important. ¹²⁹I, ¹³¹I (Radioiodine) and ¹³²I. An overview of iodine exposure in the USA (resulting from bomb tests) can be seen at. Open air nuclear testing and the Chernobyl disaster both released iodine-131.

The shortlived isotopes of iodine are particularly harmful because the thyroid collects and concentrates iodide -- radioactive as well as non-radioactive -- for use in the production of metabolic hormones. Absorption of radioiodine can lead to acute, chronic, and delayed effects. Acute effects from high doses include thyroiditis, while chronic and delayed effects include hypothyroidism, thyroid nodules, and thyroid cancer. It has been shown that the active iodine released from Chernobyl and Mayak has resulted in an increase in the incidence of thyroid cancer in the former Soviet Union.

One measure which may protect against this risk is taking large doses of potassium iodide before exposure to radioiodine -- the non-radioactive iodide 'saturates' the thyroid, causing less of the radioiodine to be stored in the body. Because this countermeasure simply takes advantage of the pharmacokinetics regarding iodide uptake, it affords no protection against other causes of radiation poisoning.

Administering potassium iodide reduces the effects of radio iodine by 99%, and is a prudent, inexpensive supplement to sheltering. The Food and Drug Administration (FDA) has approved potassium iodide as an over-the-counter medication. As with any medication, individuals should check with their doctor or pharmacist before using it.

A low-cost alternative to commercially available iodine pills is a saturated solution of potassium iodide. It usually possible to obtain several thousand doses for prices near US$ 0.01/dose. Long term storage of KI is normally in the form of reagent grade crystals, which are convenient and available commercially. The purity is superior to "pharmacologic grade". Its concentration depends only on temperature, which is easy to determine, and the required dose is easily administered by measuring the required volume of the liquid. At room temperature, the U.S. standard adult radiological protective dose of 130mg is four drops of a saturated solution. A baby's dose is 65mg, or two drops. It should be noted that these doses are sufficient to cause nausea and sometimes emesis in most individuals. It's normally administered in a ball of bread, because it tastes incredibly bad. Use is contraindicated in individual known to be allergic to iodine; for such persons sodium perchlorate is one alternative (see chap 13, Kearney).

1. Cresson Kearny, Nuclear War Survival Skills, available on line at Oregon Institute of Science and Medicine, created with the permission of the author. The information on KI is near the end of chapter 13. This manual has proven technical info on expedient fallout shelters, and assorted shelter system needs that can be created from common household items. OISM also offers free downloads of other civil defense and shelter information as well.

Caesium

The Chernobyl accident released a large amount of caesium isotopes, these were dispersed over a wide area. For instance they can be found in the soil of France at low levels while in some areas of the former Soviet Union the concentration in soil is sometimes much higher. For a review of the methods used to decontaminate an urban environment please see the scope report Behaviour and Decontamination of Artificial Radionuclides in the Urban Environment. Also see chapter four of the NEA reports Chernobyl ten years on and Chernobyl twenty years on for details of how farming methods can be changed to reduce the impact of accident fallout.

Prussian blue

In livestock farming an important countermeasure against ¹³⁷Cs is to feed to animals a little prussian blue. This iron potassium cyanide compound acts as a ion-exchanger. The cyanide is so tightly bonded to the iron that it is safe for a human to eat several grams of prussian blue per day. The prussian blue reduces the biological half life (different from the nuclear half life) of the caesium. The physical or nuclear half life of ¹³⁷Cs is about 30 years. This is a constant which can not be changed but the biological half life is not a constant. It will change according to the nature and habits of the organism it is expressed for. Caesium in humans normally has a biological half life of between one and four months. An added advantage of the prussian blue is that the caesium which is stripped from the animal in the droppings is in a form which is not available to plants. Hence it prevents the caesium from being recycled. The form of prussian blue required for the treatment of humans or animals is a special grade. Attempts to use the pigment grade used in paints have not been successful. For further details of the use of prussian blue please see the IAEA report on the Goiânia accident.

Ploughing or the removal of the top layer

¹³⁷Cs is an isotope which is of long term concern as it remains in the top layers of soil. Plants with shallow root systems tend to absorb it for many years. Hence grass and mushrooms can carry a considerable amount of ¹³⁷Cs which can be transferred to humans through the food chain. One of the best countermeasures in dairy farming against ¹³⁷Cs is to mix up the soil by deeply ploughing the soil. This has the effect of putting the ¹³⁷Cs out of reach of the shallow roots of the grass, hence the level of radioactivity in the grass will be lowered. Also after a nuclear war or serious accident the removal of top few cm of soil and its burial in a shallow trench will reduce the long term gamma dose to humans due to ¹³⁷Cs as the gamma photons will be attenuated by their passage through the soil. The deeper and more remote the trench is, the better the degree of protection which will be afforded to the human population.

Release from the Chernobyl fire

More details about the caesium release from the Chernobyl accident can be found at. A definitive report on Chernobyl is at - table 1 in chapter two lists the radioisotopes released in the fire. The percentage of the inventory which was released was controlled largely by how volatile the fission product is. Hence a greater proportion of the xenon and iodine than the cerium and plutonium were released.

Strontium

Also by the addition of lime to soils which are poor in calcium the uptake of strontium by plants can be reduced, likewise in areas where the soil is low in potassium, the addition of a potassium fertiliser can discourage the uptake of caesium into plants. However such treatments with either lime or potash should not be undertaken lightly as they can alter the soil chemistry greatly so resulting in a change in the plant ecology of the land.

Fission products within the back end of the nuclear fuel cycle

Caesium

It is known that the isotope responsible for the majority of the external gamma exposure in fuel reprocessing plants (and the Chernobyl site in 2005) is Cs-137. ¹³⁷Cs does appear to be an indicator of nuclear fission, as it is only formed by nuclear fission of an actinide.

¹³⁷Cs is often removed from waste waters in the nuclear industry by means of solid ion exchangers. A range of zeolites can be used for this task. In nuclear reactors both ¹³⁷Cs and ⁹⁰Sr are found in locations remote from the fuel, this is because these isotopes are formed by the beta decay of noble gases (xenon-137 {halflife of 3.8 minutes}and krypton-90 {halflife 32 seconds}) which enable these isotopes to be deposited in locations remote from the fuel (eg on control rods and in the space inside a fuel pin between the fuel and the cladding)

Iodine

¹³³I decays by beta particle decay (with a half life of 20.8 hours) to ¹³³Xe which in turn decays by beta decay (with a half life of 5.2 days) to ¹³³Cs. The isotopes which decay to ¹³³I are very short lived. ¹²⁹I is very long lived and this is one of the major radioactive elements which enter the sea from reprocessing plants.

Fission products which form anions

Some fission products are very long lived, examples of these include iodine-129 and technetium-99. Both of these are very mobile in solid/water as they form anionic species (Iodide and ⁹⁹TcO₄-).

Absorption of fission products on metal surfaces

Tc

It is interesting to note that in common with chromate and molybdate that ⁹⁹TcO₄- ion can react with steel surfaces to form a corrosion resistant layer. In this way these metaloxo anions act as anodic corrosion inhibitors. The formation of ⁹⁹TcO₂ on steel surfaces is one effect which will retard the release of ⁹⁹Tc from nuclear waste drums and nuclear equipment which has become lost prior to decontamination (eg submarine reactors which have been lost at sea). This ⁹⁹TcO₂ layer renders the steel surface passive, it inhibits the anodic corrosion reaction.

I

In a similar way the release of iodine-131 in a serious power reactor accident could be retarded by absorption on metal surfaces within the nuclear plant. A PhD thesis was written on this subject at The Nuclear chemistry department at Chalmers University of Technology in Sweden.

• H. Glänneskog. Interactions of I₂ and CH₃I with reactive metals under BWR severe-accident conditions, Nucl. Engineering and Design, 2004, 227, pages 323-329.

• H. Glänneskog. Iodine chemistry under severe accident conditions in a nuclear power reactor, Ph.D. Thesis, Chalmers University of Technology, October, 2005.

A lot of other work on the iodine chemistry which would occur during a bad accident has been done.

Radioactive Contamination: Environmental Radioactivity

Environmental radioactivity is the study of radioactive materials in the human environment. While some radioisotopes are only found on Earth as a result of human activity, such as Strontium-90 (⁹⁰Sr) and Technetium-99 (⁹⁹Tc), and some isotopes like Potassium-40 (⁴⁰K) are only present due to natural processes, a few isotopes are present as a result of both natural processes and human activities e.g. tritium (³H). The concentration and location of some natural isotopes, particularly Uranium-238 (²³⁸U), can be affected by human activity.

Background level in soils

Radioactivity is present everywhere (and has been since the formation of the earth). According to the IAEA, one kilogram of soil typically contains the following amounts of the following three natural radioisotopes 370 Bq ⁴⁰K (typical range 100-700 Bq), 25 Bq ²²⁶Ra (typical range 10-50 Bq), 25 Bq ²³⁸U (typical range 10-50 Bq) and 25 Bq ²³²Th (typical range 7-50 Bq). These values are average values and some soils may varry greatly from these norms.

Sea and river silt

A recent report on the Sava river in Serbia suggests that many of the river silts contain about 100 Bq kg^-1 of natural radioisotopes (²²⁶Ra, ²³²Th and ²³⁸U). Also according to the United Nations the normal concentration of uranium in soil is 300 μg kg^-1 to 11.7 mg kg^-1. It is well known that some plants are able to absorb and concentrate metals within their tissues (see hyperaccumulators for further detail) and it is known that iodine was first isolated from seaweed in France which suggests that seaweed is an iodine hyperaccumulator.

For instance Busby quotes Garland et al. 1989 who reported the plutonium activity in Welsh inter tidal sediments which suggests that the closer a site is to Sellafield the higher the concentration of plutonium in the silt is. Some relationship can be seen but the scatter of points is large (R² = 0.3683) if the data is fitted to an exponential line.

Man-made

The additional radioactivity in the biosphere caused by human activity due to the releases of man-made radioactivity and of Naturally Occurring Radioactive Materials (NORM} can be divided into several classes.

1. Normal licensed releases which occur during the regular operation of a plant or process handling man-made radioactive materials.
   • For instance the release of ⁹⁹Tc from a nuclear medicine department of a hospital which occurs when a person given a Tc imaging agent expels the agent.
2. Releases of man-made radioactive materials which occur during an industrial or research accident.
   • For instance the Chernobyl accident.
3. Releases which occur as a result of military activity.
   • For example a nuclear weapons test.
4. Releases which occur as a result of a crime.
   • For example the Goiânia accident where thieves, unaware of its radioactive content, stole some medical equipment and as a result a number of people were exposed to radiation.
5. Releases of naturally occurring radioactive materials (NORM) as a result of mining etc.
   • For example the release of the trace quantities of uranium and thorium in coal, when it is burned in power stations.

Farming and the transfer to humans of deposited radioactivity

Just because a radioisotope lands on the surface of the soil, does not mean it will enter the human food chain. After release into the environment radioactive materials can reach humans in a range of different routes, and the chemistry of the element usually dictates the most likely route.

Airborne radioactive material can have an effect on humans via a range of routes.

Cows

Jiří Hála's textbook (Radioactivity, Ionizing Radiation and Nuclear Energy, ISBN 807302053X explains how cattle only pass a minority of the strontium, caesium, plutonium and americium they ingest to the humans who consume milk and meat. For instance, for milk if the cow has a daily intake of 1000 Bq of the following isotopes then the milk will have the following activities.

• ⁹⁰Sr, 2 Bq dm^-3
• ¹³⁷Cs, 5 Bq dm^-3
• ²³⁹Pu, 0.001 Bq dm^-3
• ²⁴¹Am, 0.001 Bq dm^-3

Soil

Jiří Hála's textbook states that soils vary greatly in their ability to bind radioisotopes, the clay particles and humic acids can alter the distribution of the isotopes between the soil water and the soil. The distribution coefficient K_d is the ratio of the soil's radioactivity (Bq g^-1) to that of the soil water (Bq ml^-1). If the radioactivity is tightly bonded to by the minerals in the soil then less radioactivity can be absorbed by crops and grass growing in the soil.

• Cs-137 K_d = 1000
• Pu-239 K_d = 10000 to 100000
• Sr-90 K_d = 80 to 150
• I-131 K_d = 0.007 to 50

The trinity test

One dramatic source of man-made radioactivity is a nuclear weapons test. The glassy trinitite formed by the first atom bomb contains radioisotopes formed by neutron activation and nuclear fission. In addition some natural radioisotopes are present. A recent paper (P.P. Parekh, T.M. Semkow, M.A. Torres, D.K. Haines, J.M. Cooper, P.M. Rosenberg and M.E. Kitto, Jorunal of Environmental Radioactivity, 2006, 85, 103-120) reports the levels of long lived radioisotopes in the trinitite. The trinitite was formed from feldspar and quartz which were melted by the heat. Two samples of trinitite were used, the first (left hand side bars) was taken from between 40 and 65 meters of ground zero while the other sample was taken from further away from the ground zero point.

The ¹⁵²Eu and ¹⁵⁴Eu was mainly formed by the neutron activation of the europium in the soil, it is clear that the level of radioactivity for these isotopes is highest where the neutron dose to the soil was larger. Some of the ⁶⁰Co is generated by activation of the cobalt in the soil, but some was also generated by the activation of the cobalt in the steel (100 foot) tower. This ⁶⁰Co from the tower would have been scattered over the site reducing the difference in the soil levels.

The ¹³³Ba and ²⁴¹Am are due to the neutron activation of barium and plutonium inside the bomb. The barium was present in the form of the nitrate in the chemical explosives used while the plutonium was the fissile fuel used.

The ¹³⁷Cs level is higher in the sample which was further away from the ground zero point– this is thought to be because the precursors to the ¹³⁷Cs (¹³⁷I and ¹³⁷Xe) and the caesium to a lesser degree are volatile. The natural radioisotopes in the glass are about the same in both locations.

Activation products

The action of neutrons on stable isotopes can form radioisotopes, for instance the neutron bombardment (neutron activation) of nitrogen-14 forms carbon-14. This radioisotope can be released from the nuclear fuel cycle, this is the radioisotope responsible for the majority of the dose experienced by the population as a result of the activities of the nuclear power industry. For a discussion of the physics of neutron activation see Neutron activation analysis.

Nuclear bomb tests have increased the specific activity of carbon, whereas the use of fossil fuels has decreased it. See the page on Radiocarbon dating for further details.

Fission products

See fission products for more detail, two sources of these radioisotopes is nuclear fallout from atomic bombs and nuclear accidents such as chernobyl. For a good paper about the isotropic signature of the local bomb fallout from a ground burst see T. Imanaka, S. Fukutani, M. Yamamoto, A. Sakaguchi and M. Hoshi, J. Radiation Research, 2006, 47, Suppl A121-A127.

Discharges from plants within the nuclear fuel cycle introduce fission products to the environment, the releases from nuclear reprocessing plants tend to be medium to longlived radioisotopes, this is because the nuclear fuel is allowed to cool for several years before being dissolved in the nitric acid. The releases from nuclear reactor accidents and bomb detonations will contain a greater amount of the shortlived radioisotopes (when the amounts are expressed in activity).

Short lived

An example of a shortlived fission product is Iodine-131, this can also be formed as an activation product by the neutron activation of tellurium.

In both bomb fallout and a release from a power reactor accident, the shortlived isotopes cause the dose rate on day one to be much higher than that which will be experienced at the same site many days later. This holds true even if no attempts at decontamination are made. In the graphs below, the total gamma dose rate and the share of the dose due to each main isotope released by the Chernobyl accident are shown.

Medium lived

The classic example is ¹³⁷Cs, the caesium is released in bomb fallout and from the nuclear fuel cycle. A paper has been written on the radioactivity found in oysters found in the Irish Sea, these were found by gamma spectroscopy to contain ¹⁴¹Ce, ¹⁴⁴Ce, ¹⁰³Ru, ¹⁰⁶Ru, ¹³⁷Cs, ⁹⁵Zr and ⁹⁵Nb. In addition a zinc activation product (⁶⁵Zn) was found, this is thought to be due to the corrosion of magnox fuel cladding in cooling ponds. It is likely that the modern releases of all these isotopes from Windscale is smaller.

An important part of the Chernobyl release was the caesium-137, this isotope is responsible for much of the long term (at least one year after the fire) external exposure which has occurred at the site. Also the caesium isotopes in the fallout have had an effect on farming.

A good source of data on the subject of caesium in Chernobyl fallout exists at, this is the Ukrainian Research Institute for Agricultural Radiology.

A great deal of caesium was released during the Goiânia accident where a radioactive source (made for medical use) was stolen and then smashed open during an attempt to convert it into scrap metal. The accident could have been stopped at several stages; first, the last legal owners of the source failed to make arrangements for the source to be stored in a safe and secure place; and second, the scrap metal workers who took it did not recognise the markings which indicated that it was a radioactive object.

P. Soudek, Š. Valenová, Z. Vavříková and T. Vaněk, Journal of Environmental Radioactivity, 2006, 88, 236-250 report details of the uptake of ⁹⁰Sr and ¹³⁷Cs into sunflowers grown under hydroponic conditions. The caesium was found in the leaf veins, in the stem and in the apical leaves. It was found that 12% of the caesium entered the plant, and 20% of the strontium. This paper also reports details of the effect of potassium, ammonium and calcium ions on the uptake of the radioisotopes.

Caesium binds tightly to clay minerals such as illite and montmorillonite; hence it remains in the upper layers of soil where it can be accessed by plants with shallow roots (such as grass). Hence grass and mushrooms can carry a considerable amount of ¹³⁷Cs which can be transferred to humans through the food chain. One of the best countermeasures in dairy farming against ¹³⁷Cs is to mix up the soil by deeply ploughing the soil. This has the effect of putting the ¹³⁷Cs out of reach of the shallow roots of the grass, hence the level of radioactivity in the grass will be lowered. Also after a nuclear war or serious accident the removal of top few cm of soil and its burial in a shallow trench will reduce the long term gamma dose to humans due to ¹³⁷Cs as the gamma photons will be attenuated by their passage through the soil. The more remote the trench is from humans and the deeper the trench is the better the degree of protection which will be afforded to the human population.

In livestock farming an important countermeasure against ¹³⁷Cs is to feed to animals a little prussian blue. This iron potassium cyanide compound acts as an ion-exchanger. The cyanide is so tightly bonded to the iron that it is safe for a human to eat several grams of prussian blue per day. The prussian blue reduces the biological half life (different from the nuclear half life) of the caesium. The physical or nuclear half life of ¹³⁷Cs is about 30 years. This is a constant which can not be changed but the biological half life is not a constant. It will change according to the nature and habits of the organism for which it is expressed. Caesium in humans normally has a biological half life of between one and four months. An added advantage of the prussian blue is that the caesium which is stripped from the animal in the droppings is in a form which is not available to plants. Hence it prevents the caesium from being recycled. The form of prussian blue required for the treatment of humans or animals is a special grade. Attempts to use the pigment grade used in paints have not been successful.

Long lived

A pair of good examples would be iodine-129 and Tc-99.

Plutonium and the other actinides

In popular culture plutonium is credited with being the ultimate threat to life and limb which is wrong; while ingesting plutonium is not likely to be good for one's health, other radioisotopes such as radium are more toxic to humans. Regardless, the introduction of the transuranium elements such as plutonium into the environment should be avoided wherever possible. Currently the activities of the nuclear reprocessing industry have been subject to great debate as one of the fears of those opposed to the industry is that large amounts of plutonium will be either mismanaged or released into the environment. In the past one of the biggest releases of plutonium into the environment has been nuclear bomb testing.

• Those tests in the air scattered some plutonium over the entire globe; this great dilution of the plutonium has resulted in the threat to each exposed person being very small as each person is only exposed to a very small amount.
• The underground tests tend to form molten rock which rapidly cools and seals in the actinides so rendering them unable to move, again the threat to humans is small unless the site of the test is dug up.
• The safety trials where bombs were subject to simulated accidents pose the greatest threat to people; some areas of land used for such experiments (conducted in the open air) have not been fully released for general use despite in one case an extensive decontamination.

Natural

Activation products from cosmic rays

Cosmogenic isotopes (or cosmogenic nuclides) are rare isotopes created when a high-energy cosmic ray interacts with the nucleus of an in situ atom. These isotopes are produced within earth materials such as rocks or soil, in Earth's atmosphere, and in extraterrestrial items such as meteorites. By measuring cosmogenic isotopes, scientists are able to gain insight into a range of geological and astronomical processes. There are both radioactive and stable cosmogenic isotopes. Some of these radioisotopes are tritium, carbon-14 and phosphorus-32.

Production modes

Here is a list of radioisotopes formed by the action of cosmic rays on the atomosphere, the list also contains the production mode of the isotope. These data were obtained from the SCOPE50 report, see table 1.9 of chapter 1.

Isotopes formed by the action of cosmic rays on the air

Isotope	Mode of formation
³H (tritium)	14N (n, 12C)³H
7Be	Spallation (N and O)
10Be	Spallation (N and O)
11C	Spallation (N and O)
14C	14N (n, p) 14C
18F	18O (p, n)18F and Spallation (Ar)
22Na	Spallation (Ar)
24Na	Spallation (Ar)
28Mg	Spallation (Ar)
31Si	Spallation (Ar)
32Si	Spallation (Ar)
32P	Spallation (Ar)
34mCl	Spallation (Ar)
35S	Spallation (Ar)
36Cl	35Cl (n, )36Cl
37Ar	37Cl (p, n)37Ar
38Cl	Spallation (Ar)
38	Spallation (Ar)
39Ar	38Ar (n, )39Ar
39Cl	40Ar (n, np)39Cl & spallation (Ar)
41Ar	40Ar (n, )41Ar
81Kr	80Kr (n, ) 81Kr

Transfer to ground

The level of beryllium-7 in the air is related to the sun spot cycle, as radiation from the sun forms this radioisotope in the atmosphere. The rate at which it is transferred from the air to the ground is controlled in part by the weather.

Applications in geology listed by isotope

Commonly measured long lived cosmogenic isotopes

element	mass	half-life (years)	typical application
helium	3	- stable -	exposure dating of olivine-bearing rocks
beryllium	10	1.36 million	exposure dating of quartz-bearing rocks, sediment, dating of ice cores, measurement of erosion rates
carbon	14	5,730	dating of organic matter, water
neon	21	- stable -	dating of very stable, long-exposed surfaces, including meteorites
aluminum	26	720,000	exposure dating of rocks, sediment
chlorine	36	308,000	exposure dating of rocks, groundwater tracer
calcium	41	103,000	exposure dating of carbonate rocks
iodine	129	15.7 million	groundwater tracer

Applications of dating

Because cosmogenic isotopes have long half-lives (anywhere from thousands to millions of years), scientists find them useful for geologic dating. Cosmogenic isotopes are produced at or near the surface of the Earth, and thus are commonly applied to problems of measuring ages and rates of geomorphic and sedimentary events and processes.

Specific applications of cosmogenic isotopes include:

• exposure dating of earth surfaces, including glacially-scoured bedrock, fault scarps, landslide debris
• burial dating of sediment, bedrock, ice
• measurement of steady-state erosion rates
• absolute dating of organic matter (radiocarbon dating)
• absolute dating of water masses, measurement of groundwater transport rates
• absolute dating of meteorites, lunar surfaces

Methods of measurement for the long lived isotopes

To measure cosmogenic isotopes produced within solid earth materials, such as rock, samples are generally first put through a process of mechanical separation. The sample is crushed and desirable material, such as a particular mineral (quartz in the case of Be-10), is separated from non-desirable material by using a density separation in a heavy liquid medium such as LST (lithium sodium tungstate).

The sample is then dissolved, a common isotope carrier added (Be-9 carrier in the case of Be-10), and the aqueous solution is purified down to an oxide or other pure solid.

Finally, the ratio of the rare cosmogenic isotope to the common isotope is measured using accelerator mass spectrometry. The original concentration of cosmogenic isotope in the sample is then calculated using the measured isotopic ratio, the mass of the sample, and the mass of carrier added to the sample.

Radioactive Contamination: Actinides in the Environment

Actinides in the environment refer to the sources, environmental behaviour and effects of actinides in the environment. Environmental radioactivity is not limited solely to actinides; also, actinides such as uranium and radium specifically are of note.

Inhalation versus ingestion

In general for the insoluble actinide oxides such as high fired uranium dioxide and MOX fuel if it is swallowed then it will pass through the digestive system with very little actinide dissolving. As the actinide oxide can not dissolve, it can not be absorbed into the body of the person or animal. With such an oxide the dose a person is committed to after a given intake of activity is higher for inhalation than for ingestion as the insoluble compound will remain in the lungs, where it will then irradiate the lung tissue.

Low fired oxides and soluble salts such as the nitrates can be absorbed with greater ease through the digestive system, so they are able to enter the bloodstream after being swallowed. If they are inhaled then it is possible for the solid to dissolve and leave the lungs. Hence the dose to the lungs will be lower for the soluble form.

Radon and radium in the environment

Radon and radium are not actinides—they are both radioactive daughters from the decay of uranium. Aspects of their biology and environmental behaviour is discussed at radium in the environment.

Thorium in the environment

In India, a large amount of thorium ore can be found in the form of monazite in placer deposits of the Western and Eastern coastal dune sands, particularly in the Tamil Nadu coastal areas. The residents of this area are exposed to a naturally occurring radiation dose ten times higher than the worldwide average.

Occurrence

Thorium is found in small amounts in most rocks and soils, where it is about three times more abundant than uranium, and is about as common as lead. Soil commonly contains an average of around 6 parts per million (ppm) of thorium. Thorium occurs in several minerals, the most common being the rare earth-thorium-phosphate mineral, monazite, which contains up to about 12% thorium oxide. There are substantial deposits in several countries. ²³²Th decays very slowly (its half-life is about three times the age of the earth) but other thorium isotopes occur in the thorium and uranium decay chains. Most of these are short-lived and hence much more radioactive than ²³²Th, though on a mass basis they are negligible.

Effects in humans

Thorium has been linked to liver cancer. In the past thoria (thorium dioxide) was used as a contrast agent for medical X-ray radiography but its use has been discontinued. It was sold under the name Thorotrast.

Uranium in the environment

Uranium is a natural metal which is widely found. It is present in almost all soils and it is more plentiful than antimony, beryllium, cadmium, gold, mercury, silver, or tungsten and is about as abundant as arsenic or molybdenum. Significant concentrations of uranium occur in some substances such as phosphate rock deposits, and minerals such as lignite, and monazite sands in uranium-rich ores (it is recovered commercially from these sources).

Seawater contains about 3.3 parts per billion of uranium by weight as uranium(VI) forms soluble carbonate complexes. The extraction of uranium from seawater has been considered as a means of obtaining the element. Due to the very low specific activity of uranium the chemical effects of it upon living things can often outweigh the effects of its radioactivity. Additional uranium has been added to the environment in some locations as a result of the nuclear fuel cycle and the use of depleted uranium in munitions.

Neptunium in the environment

Like plutonium, neptunium has a high affinity for soil. However, it is relatively mobile over the long term, and diffusion of neptunium-237 in groundwater is a major issue in designing a deep geological repository for permanent storage of spent nuclear fuel. ²³⁷Np has a halflife of 2.144 million years, so it is a long-term problem; but its halflife is still much shorter than those of uranium-238, uranium-235, or uranium-236, and ²³⁷Np therefore has higher specific activity than those nuclides.

Americium in the environment

Americium often enters landfills from discarded smoke detectors. The rules associated with the disposal of smoke detectors are very relaxed in most municipalities. For instance in the UK it is permissible to dispose of an americium containing smoke detector by placing it in the dustbin with normal household rubbish, but each dustbin worth of rubbish is limited to only containing one smoke detector.

In France a truck transporting 900 smoke detectors had been reported to have caught fire, it is claimed that this led to a release of americium into the environment. In the U.S., the "Radioactive Boy Scout" David Hahn was able to buy thousands of smoke detectors at remainder prices and concentrate the americium from them.

There have been cases of humans being contaminated with americium, the worst case being that of Harold McCluskey. It is interesting to note that Harold McCluskey did not die of cancer but of heart disease (which he had before the accident). It is likely that the medical care which he was given saved his life; it should be noted that due to the difference in the chemistry of americium (the +3 oxidation state is very stable) to plutonium (where the +4 state can form in the human body) the americium has very different biochemistry to plutonium.

The most common isotope americium-241 decays (halflife 431 years) to neptunium-237 which has a much longer halflife, so in the long term, the issues discussed above for neptunium apply.

Plutonium in the environment

Sources

Plutonium in the environment has several sources. These include:

• Atomic batteries
  • In space
  • In pacemakers
• Bomb detonations
• Bomb safety trials
• Nuclear accidents (such as Chernobyl)
• Nuclear crime
• Nuclear fuel cycle

Environmental chemistry

Plutonium, like other actinides, readily forms a dioxide plutonyl core (PuO₂). In the environment, this plutonyl core readily complexes with carbonate as well as other oxygen moieties (OH^-, NO₂^-, NO₃^-, and SO₄^-2) to form charged complexes which can be readily mobile with low affinities to soil.

• PuO₂(CO₃)₁^-2
• PuO₂(CO₃)₂^-4
• PuO₂(CO₃)₃^-6

PuO₂ formed from neutralizing highly acidic nitric acid solutions tends to form polymeric PuO₂ which is resistant to complexation. Plutonium also readily shifts valences between the +3, +4, +5 and +6 states. It is common for some fraction of plutonium in solution to exist in all of these states in equilibrium.

Plutonium is known to bind to soil particles very strongly, see above for a X-ray spectrscopic study of plutonium in soil and concrete. While caesium has very different chemistry to the actinides, it is well known that both caesium and many of the actinides bind strongly to the minerals in soil. Hence it has been possible to use ¹³⁴Cs labeled soil to study the migration of Pu and Cs is soils. It has been shown that colloidal transport processes control the migration of Cs (and will control the migration of Pu) in the soil at the Waste Isolation Pilot Plant.

Soil Contamination: Pesticide

A pesticide is a substance or mixture of substances used to kill a pest. A pesticide may be a chemical substance, biological agent (such as a virus or bacteria), antimicrobial, disinfectant or device used against any pest. Pests include insects, plant pathogens, weeds, molluscs, birds, mammals, fish, nematodes (roundworms) and microbes that compete with humans for food, destroy property, spread or are a vector for disease or cause a nuisance. Although there are benefits to the use of pesticides, there are also drawbacks, such as potential toxicity to humans and other animals.

Types of pesticides

There are multiple ways of classifying pesticides.

• Algicides or Algaecides for the control of algae
• Avicides for the control of birds
• Bactericides for the control of bacteria is motored to a car

• Fungicides for the control of fungi and oomycetes
• Herbicides for the control of weeds
• Insecticides for the control of insects - these can be Ovicides (substances that kill eggs), Larvicides (substances that kill larvae) or Adulticides (substances that kill adult insects)
• Miticides or Acaricides for the control of mites
• Molluscicides for the control of slugs and snails
• Nematicides for the control of nematodes
• Rodenticides for the control of rodents
• Virucides for the control of viruses (e.g. H5N1)

Pesticides can also be classed as synthetic pesticides or biological pesticides (biopesticides), although the distinction can sometimes blur.

Broad-spectrum pesticides are those that kill an array of species, while narrow-spectrum, or selective pesticides only kill a small group of species.

A systemic pesticide moves inside a plant following absorption by the plant. With insecticides and most fungicides, this movement is usually upward (through the xylem) and outward. Increased efficiency may be a result. Systemic insecticides which poison pollen and nectar in the flowers may kill needed pollinators such as bees.

Most pesticides work by poisoning pests.

Uses of pesticide

Pesticides are used to control organisms which are considered harmful. For example, they are used to kill mosquitoes that can transmit potentially deadly diseases like west nile virus, yellow fever, and malaria. They can also kill bees, wasps or ants that can cause allergic reactions. Insecticides can protect animals from illnesses that can be caused by parasites such as fleas. Pesticides can prevent sickness in humans that could be caused by mouldy food or diseased produce. Herbicides can be used to clear roadside weeds, trees and brush. They can also kill invasive weeds in parks and wilderness areas which may cause environmental damage. Herbicides are commonly applied in ponds and lakes to control algae and plants such as water grasses that can interfere with activities like swimming and fishing and cause the water to look or smell unpleasant. Uncontrolled pests such as termites and mould can damage structures such as houses. Pesticides are used in grocery stores and food storage facilities to manage rodents and insects that infest food such as grain. Each use of a pesticide carries some associated risk. Proper pesticide use decreases these associated risks to a level deemed acceptable by pesticide regulatory agencies such as the United States Environmental Protection Agency (EPA) and the Pest Management Regulatory Agency (PMRA) of Canada.

Pesticides can save farmers money by preventing crop losses to insects and other pests; in the US, farmers get an estimated fourfold return on money they spend on pesticides. One study found that not using pesticides reduced crop yields by about 10%. Another study,conducted in 1999, found that a ban on pesticides in the United States may result in a rise of food prices, loss of jobs, and an increase in world hunger.

DDT, sprayed on the walls of houses, is an organochloride that has been used to fight malaria since the 1950s. Recent policy statements by the World Health Organization have given stronger support to this approach. Dr. Arata Kochi, WHO's malaria chief, said, "One of the best tools we have against malaria is indoor residual house spraying. Of the dozen insecticides WHO has approved as safe for house spraying, the most effective is DDT". However, since then, an October 2007 study has linked breast cancer from exposure to DDT prior to puberty. Poisoning may also occur due to use of DDT and other chlorinated hydrocarbons by entering the human food chain when animal tissues are affected. Symptoms include nervous excitement, tremors, convulsions or death. Scientists estimate that DDT and other chemicals in the organophosphate class of pesticides have saved 7 million human lives since 1945 by preventing the transmission of diseases such as malaria, bubonic plague, sleeping sickness, and typhus. However, DDT use is not always effective, as resistance to DDT was identified in Africa as early as 1955, and by 1972 nineteen species of mosquito worldwide were resistant to DDT. A study for the World Health Organization in 2000 from Vietnam established that non-DDT malaria controls were significantly more effective than DDT use. The ecological effect of DDT on organisms is an example of bioaccumulation.

History of pesticide

Since before 2500 BCE, humans have utilized pesticides to protect their crops. The first known pesticide was elemental sulfur dusting used in Sumeria about 4,500 years ago. By the 15th century, toxic chemicals such as arsenic, mercury and lead were being applied to crops to kill pests. In the 17th century, nicotine sulfate was extracted from tobacco leaves for use as an insecticide. The 19th century saw the introduction of two more natural pesticides, pyrethrum which is derived from chrysanthemums, and rotenone which is derived from the roots of tropical vegetables.

In 1939, Paul Müller discovered that DDT was a very effective insecticide. It quickly became the most widely-used pesticide in the world.

In the 1940s manufacturers began to produce large amounts of synthetic pesticides and their use became widespread. Some sources consider the 1940s and 1950s to have been the start of the "pesticide era". Pesticide use has increased 50-fold since 1950 and 2.3 million tonnes (2.5 million imperial tons) of industrial pesticides are now used each year. Seventy-five percent of all pesticides in the world are used in developed countries, but use in developing countries is increasing.

In the 1960s, it was discovered that DDT was preventing many fish-eating birds from reproducing, which was a serious threat to biodiversity. Rachel Carson wrote the best-selling book Silent Spring about biological magnification. The agricultural use of DDT is now banned under the Stockholm Convention on Persistent Organic Pollutants, but it is still used in some developing nations to prevent malaria and other tropical diseases by spraying on interior walls to kill or repel mosquitoes.

Regulation

In most countries, in order to sell or use a pesticide, it must be approved by a government agency. For example, in the United States, the Environmental Protection Agency (EPA) does so. Complex and costly studies must be conducted to indicate whether the material is safe to use and effective against the intended pest. During the registration process, a label is created which contains directions for the proper use of the material. Based on acute toxicity, pesticides are assigned to a Toxicity Class.

Some pesticides are considered too hazardous for sale to the general public and are designated restricted use pesticides. Only certified applicators, who have passed an exam, may purchase or supervise the application of restricted use pesticides. Records of sales and use are required to be maintained and may be audited by government agencies charged with the enforcement of pesticide regulations.

In Canada, over 140 municipalities and the entire province of Quebec have now placed restrictions on the cosmetic use of synthetic lawn pesticides as a result of health and environmental concerns. The Ontario provincial government promised on September 24, 2007 to also implement a province-wide ban on the cosmetic use of lawn pesticides, for protecting the public. Medical and environmental groups support such a ban. On April 22, 2008, the Provincial Government of Ontario announced that it will pass legislation that will prohibit, province-wide, the cosmetic use and sale of lawn and garden pesticides. The Ontario legislation would also echo Massachusetts law requiring pesticide manufacturers to reduce the toxins they use in production. The Province of Prince Edward Island is also considering such legislation. On April 3, 2008, the Canadian Cancer Society released opinion poll results conducted by Ipsos Reid, which established that a clear majority of residents in the provinces of British Columbia and Saskatchewan want province-wide cosmetic lawn pesticide bans, and that the majority of respondents believe that cosmetic pesticides are a threat to their health.

Though pesticide regulations differ from country to country, pesticides and products on which they were used are traded across international borders. To deal with inconsistencies in regulations among countries, delegates to a conference of the United Nations Food and Agriculture Organization adopted an International Code of Conduct on the Distribution and Use of Pesticides in 1985 to create voluntary standards of pesticide regulation for different countries. The Code was updated in 1998 and 2002. The FAO claims that the code has raised awareness about pesticide hazards and decreased the number of countries without restrictions on pesticide use.

Two other efforts to improve regulation of international pesticide trade are the United Nations London Guidelines for the Exchange of Information on Chemicals in International Trade and the United Nations Codex Alimentarius Commission. The former seeks to implement procedures for ensuring that prior informed consent exists between countries buying and selling pesticides, while the latter seeks to create uniform standards for maximum levels of pesticide residues among participating countries. Both initiatives operate on a voluntary basis.

Reading and following label directions is required by law in countries such as the US and in limited parts of the rest of the world.

One study found pesticide self-poisoning the method of choice in one third of suicides worldwide, and recommended, among other things, more restrictions on the types of pesticides that are most harmful to humans.

Environmental effects of pesticide

Pesticide use raises a number of environmental concerns. Over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species, including non-target species, air, water, bottom sediments, and food. Pesticide drift occurs when pesticides suspended in the air as particles are carried by wind to other areas, potentially contaminating them. Pesticides are one of the causes of water pollution, and some pesticides are persistent organic pollutants and contribute to soil contamination.

Health effects of pesticide

Pesticides can present danger to consumers, bystanders, or workers during manufacture, transport, or during and after use.

The American Medical Association recommends limiting exposure to pesticides and using safer alternatives:

Particular uncertainty exists regarding the long-term effects of low-dose pesticide exposures. Current surveillance systems are inadequate to characterize potential exposure problems related either to pesticide usage or pesticide-related illnesses considering these data gaps, it is prudent o limit pesticide exposures and to use the least toxic chemical pesticide or non-chemical alternative.

Farmers and workers

There have been many studies of farmers with the goal of determining the health effects of pesticide exposure.

The World Health Organisation and the UN Environment Programme estimate that each year, 3 million workers in agriculture in the developing world experience severe poisoning from pesticides, about 18,000 of whom die. According to one study, as many as 25 million workers in developing countries may suffer mild pesticide poisoning yearly.

Organophosphate pesticides have increased in use, because they are less damaging to the environment and they are less persistent than organochlorine pesticides. These are associated with acute health problems for workers that handle the chemicals, such as abdominal pain, dizziness, headaches, nausea, vomiting, as well as skin and eye problems. Additionally, many studies have indicated that pesticide exposure is associated with long-term health problems such as respiratory problems, memory disorders, dermatologic conditions, cancer, depression, neurological deficits, miscarriages, and birth defects. Summaries of peer-reviewed research have examined the link between pesticide exposure and neurologic outcomes and cancer, perhaps the two most significant things resulting in organophosphate-exposed workers.

According to researchers from the National Institutes of Health (NIH), licensed pesticide applicators who used chlorinated pesticides on more than 100 days in their lifetime were at greater risk of diabetes. In a paper appearing in the May, 2008, issue of the American Journal of Epidemiology, researchers said the associations between specific pesticides and incident diabetes ranged from a 20 percent to a 200 percent increase in risk. New cases of diabetes were reported by 3.4 percent of those in the lowest pesticide use category compared with 4.6 percent of those in the highest category. Risks were greater when users of specific pesticides were compared with applicators who never applied that chemical.

Consumers

There are concerns that pesticides used to control pests on food crops are dangerous to people who consume those foods. These concerns are one reason for the organic food movement. Many food crops, including fruits and vegetables, contain pesticide residues after being washed or peeled. Chemicals that are no longer used but which are resistant to breakdown for long periods may remain in soil and water and thus in food.

The United Nations Codex Alimentarius Commission has recommended international standards for Maximum Residue Limits (MRLs), for individual pesticides in food.

In the EU, MRLs are set by DG-SANCO. In the US, levels of residues that remain on foods are limited to tolerance levels that are established by the U.S. Environmental Protection Agency‎ and are considered safe. The EPA sets the tolerances based on the toxicity of the pesticide and its breakdown products, the amount and frequency of pesticide application, and how much of the pesticide (i.e., the residue) remains in or on food by the time it is marketed and prepared. Tolerance levels are obtained using scientific risk assessments that pesticide manufacturers are required to produce by conducting toxicological studies, exposure modeling and residue studies before a particular pesticide can be registered, however, the effects are tested for single pesticides, and there is little information on possible synergistic effects of exposure to multiple pesticide traces in the air, food and water.

A study published by the United States National Research Council in 1993 determined that for infants and children, the major source of exposure to pesticides is through diet. A study in 2006 measured the levels of organophosphorus pesticide exposure in 23 school children before and after replacing their diet with organic food (food grown without synthetic pesticides). In this study it was found that levels of organophosphorus pesticide exposure dropped dramatically and immediately when the children switched to an organic diet.

To reduce the amounts of pesticide residues in food, consumers can wash, peel, and cook their food; trim the fat from meat; and eat a variety of foods to avoid repeat exposure to a pesticide typically used on a given crop. Consumers can also buy food that is grown organically, though even organic food may have traces of pesticides.

Strawberries and tomatoes are the two crops with the most intensive use of soil fumigants. They are particularly vulnerable to several type of diseases, insects, mites, and parasitic worms. In 2003, in California alone, 3.7 million pounds of metam sodium were used on tomatoes. In recent years other farmers have demonstrated that it is possible to produce strawberries and tomatoes without the use of harmful chemicals and in a cost effective way.

The public

Exposure routes other than consuming food that contains residues, in particular pesticide drift, are potentially significant to the general public.

The Bhopal disaster occurred when a pesticide plant released 40 tons of methyl isocyanate (MIC) gas, a chemical intermediate in the synthesis of some carbamate pesticides. The disaster immediately killed nearly 3,000 people and ultimately caused at least 15,000 deaths.

In China, an estimated half million people are poisoned by pesticides each year, 500 of whom die.

Children have been found to be especially susceptible to the harmful effects of pesticides. A number of research studies have found higher instances of brain cancer, leukemia and birth defects in children with early exposure to pesticides, according to the Natural Resources Defense Council. Often used for ridding school buildings of rodents, insects, pests, etc., pesticides only work temporarily and must be re-applied. The poisons found in pesticides are not selectively harmful to just pests and in everyday school environments children (and faculty) are exposed to high levels of pesticides and cleaning materials. "No testing has ever been done specifically pertaining to threats among children".

Peer-reviewed studies now suggest neurotoxic effects on developing animals from organophosphate pesticides at legally-tolerable levels, including fewer nerve cells, lower birth weights, and lower cognitive scores. The United States Environmental Protection Agency‎ finished a 10 year review of the organophosphate pesticides following the 1996 Food Quality Protection Act, but did little to account for developmental neurotoxic effects, drawing strong criticism from within the agency and from outside researchers.

Some scientists think that exposure to pesticides in the uterus may have negative effects on a fetus that may manifest as problems such as growth and behavioral disorders or reduced resistance to pesticide toxicity later in life.

A new study conducted by the Harvard School of Public Health in Boston, has discovered a 70% increase in the risk of developing Parkinson's disease for people exposed to even low levels of pesticides.

A 2008 study from Duke University found that the Parkinson's patients were 61 percent more likely to report direct pesticide application than were healthy relatives. Both insecticides and herbicides significantly increased the risk of Parkinson's disease.

One study found that use of pesticides may be behind the finding that the rate of birth defects such as missing or very small eyes is twice as high in rural areas as in urban areas. Another study found no connection between eye abnormalities and pesticides.

Pyrethrins, insecticides commonly used in common bug killers, can cause a potentially deadly condition if breathed in.

Continuing development

Pesticide safety education and pesticide applicator regulation are designed to protect the public from pesticide misuse, but do not eliminate all misuse. Reducing the use of pesticides and choosing less toxic pesticides may reduce risks placed on society and the environment from pesticide use. Integrated pest management, the use of multiple approaches to control pests, is becoming widespread and has been used with success in countries such as Indonesia, China, Bangladesh, the US, Australia, and Mexico. IPM attempts to recognize the more widespread impacts of an action on an ecosystem, so that natural balances are not upset. New pesticides are being developed, including biological and botanical derivatives and alternatives that are thought to reduce health and environmental risks. In addition, applicators are being encouraged to consider alternative controls and adopt methods that reduce the use of chemical pesticides.

Pesticides can be created that are targeted to a specific pest's life cycle, which can be more environmentally-friendly. For example, potato cyst nematodes emerge from their protective cysts in response to a chemical excreted by potatoes; they feed on the potatoes and damage the crop. A similar chemical can be applied to fields early, before the potatoes are planted, causing the nematodes to emerge early and starve in the absence of potatoes.

Alternatives

Alternatives to pesticides are available and include methods of cultivation, use of Biological controls,such as pheromones and microbial pesticides, and genetic engineering, and methods of interfering with insect breeding. These methods are becoming increasingly popular and often are safer than traditional chemical pesticides. In addition, EPA is registering reduced-risk conventional pesticides in increasing numbers.

Cultivation practices include polyculture (growing multiple types of plants), crop rotation, planting crops in areas where the pests that damage them do not live, timing planting according to when pests will be least problematic, and use of trap crops that attract pests away from the real crop. In the US, farmers have had success controlling insects by spraying with hot water at a cost that is about the same as pesticide spraying.

Release of other organisms that fight the pest is another example of an alternative to pesticide use. These organisms can include natural predators or parasites of the pests. Biological pesticides based on entomopathogenic fungi, bacteria and viruses cause disease in the pest species can also be used.

Interfering with insects' reproduction can be accomplished by sterilizing males of the target species and releasing them, so that they mate with females but do not produce offspring. This technique was first used on the screwworm fly in 1958 and has since been used with the medfly, the tsetse fly, and the gypsy moth. However, this can be a costly, time consuming approach that only works on some types of insects.

In India, traditional pest control methods include using Panchakavya, the "mixture of five products." The method has recently experienced a resurgence in popularity due in part to use by the organic farming community.

Some evidence shows that alternatives to pesticides can be equally effective as the use of chemicals. For example, Sweden has halved its use of pesticides with hardly any reduction in crops. In Indonesia, farmers have reduced pesticide use on rice fields by 65% and experienced a 15% crop increase.

Soil Contamination: Herbicide

A herbicide is used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant hormones. Herbicides used to clear waste ground, industrial sites, railways and railway embankments are non-selective and kill all plant material with which they come into contact. Some plants produce natural herbicides, such as the genus Juglans (walnuts). They are applied in total vegetation control (TVC) programs for maintenance of highways and railroads. Smaller quantities are used in forestry, pasture systems, and management of areas set aside as wildlife habitat.

Herbicides are widely used in agriculture and in landscape turf management. In the U.S., they account for about 70% of all agricultural pesticide use.

History of herbicide

Prior to the widespread use of chemical herbicides, cultural controls, such as altering soil pH, salinity, or fertility levels, were used to control weeds. Mechanical control (including tillage) was also (and still is) used to control weeds.

The first widely used herbicide was 2,4-dichlorophenoxyacetic acid, often abbreviated 2,4-D. It was first commercialized by the Sherwin-Williams Paint company and saw use in the late 1940s. It is easy and inexpensive to manufacture, and kills many broadleaf plants while leaving grasses largely unaffected (although high doses of 2,4-D at crucial growth periods can harm grass crops such as maize or cereals). The low cost of 2,4-D has led to continued usage today and it remains one of the most commonly used herbicides in the world. Like other acid herbicides, current formulations utilize either an amine salt (usually trimethylamine) or one of many esters of the parent compound. These are easier to handle than the acid.

2,4-D exhibits relatively good selectivity, meaning, in this case, that it controls a wide number of broadleaf weeds while causing little to no injury to grass crops at normal use rates. A herbicide is termed selective if it affects only certain types of plants, and nonselective if it inhibits a very broad range of plant types. Other herbicides have been more recently developed that achieve higher levels of selectivity than 2,4-D.

The 1950s saw the introduction of the triazine family of herbicides, which includes atrazine, which have current distinction of being the herbicide family of greatest concern regarding groundwater contamination. Atrazine does not break down readily (within a few weeks) after being applied to soils of above neutral pH. Under alkaline soil conditions atrazine may be carried into the soil profile as far as the water table by soil water following rainfall causing the aforementioned contamination. Atrazine is said to have carryover, a generally undesirable property for herbicides.

Glyphosate, frequently sold under the brand name Roundup, was introduced in 1974 for non-selective weed control. It is now a major herbicide in selective weed control in growing crop plants due to the development of crop plants that are resistant to it. The pairing of the herbicide with the resistant seed contributed to the consolidation of the seed and chemistry industry in the late 1990s.

Many modern chemical herbicides for agriculture are specifically formulated to decompose within a short period after application. This is desirable as it allows crops which may be affected by the herbicide to be grown on the land in future seasons. However, herbicides with low residual activity (i.e., that decompose quickly) often do not provide season-long weed control.

Health effects of herbicide

Certain herbicides affect metabolic pathways and systems unique to plants and not found in animals making many modern herbicides among the safest crop protection products having essentially no effect on mammals, birds, amphibians or reptiles.

Some herbicides cause a range of health effects ranging from skin rashes to death Template:Ref needed. The pathway of attack can arise from intentional or unintentional direct consumption, improper application resulting in the herbicide coming into direct contact with people or wildlife, inhalation of aerial sprays, or food consumption prior to the labeled pre-harvest interval. Under extreme conditions herbicides can also be transported via surface runoff to contaminate distant water sources. Most herbicides decompose rapidly in soils via soil microbial decomposition, hydrolysis, or photolysis. Some herbicides are more persistent with longer soil half-lives Template:Ref needed. Other alleged health effects include chest pain, headaches, nausea, and fatigue.

All organic and non-organic herbicides must be extensively tested prior to approval for commercial sale and labeling by the Environmental Protection Agency. However, because of the large number of herbicides in use, there is significant concern regarding health effects. Some of the herbicides in use are known to be mutagenic, carcinogenic or teratogenic {ref needed}.

Some herbicides may have therapeutic uses. There is current research into the use of herbicides as an anti-malaria drug that targets the plant-like apicoplast plastid in the malaria-causing parasite Plasmodium falciparum.

Classification of herbicides

Herbicides can be grouped by activity, use, chemical family, mode of action, or type of vegetation controlled.

By activity:

• Contact herbicides destroy only the plant tissue in contact with the chemical. Generally, these are the fastest acting herbicides. They are less effective on perennial plants, which are able to regrow from rhizhomes, roots or tubers.

• Systemic herbicides are translocated through the plant, either from foliar application down to the roots, or from soil application up to the leaves. They are capable of controlling perennial plants and may be slower acting but ultimately more effective than contact herbicides.

By use:

• Soil-applied herbicides are applied to the soil and are taken up by the roots and/or hypocotyl of the target plant. The following two categories are examples of soil-applied herbicides.

• Pre-plant incorporated herbicides are soil applied prior to planting and mechanically incorporated into the soil. The objective for incorporation is to prevent dissipation through photo decomposition and/or volatility.

• Preemergent herbicides are applied to the soil before the crop emerges and prevent germination or early growth of weed seeds.

• Post-emergent herbicides are applied after the crop has emerged.

Their classification by mechanism of action (MOA) indicates the first enzyme, protein, or biochemical step affected in the plant following application. The main mechanisms of action are:

• ACCase inhibitors are compounds that kill grasses. Acetyl coenzyme A carboxylase (ACCase) is part of the first step of lipid synthesis. Thus, ACCase inhibitors affect cell membrane production in the meristems of the grass plant. The ACCases of grasses are sensitive to these herbicides, whereas the ACCases of dicot plants are not.

• ALS inhibitors: the acetolactate synthase (ALS) enzyme (also known as acetohydroxyacid synthase, or AHAS) is the first step in the synthesis of the branched-chain amino acids (valine, leucine, and isoleucine). These herbicides slowly starve affected plants of these amino acids which eventually leads to inhibition of DNA synthesis. They affect grasses and dicots alike. The ALS inhibitor family includes sulfonylureas (SUs), imidazolinones (IMIs), triazolopyrimidines (TPs), pyrimidinyl oxybenzoates (POBs), and sulfonylamino carbonyl triazolinones (SCTs). ALS is a biological pathway that exists only in plants and not in animals thus making the ALS-inhibitors among the safest herbicides.

• EPSPS inhibitors: The enolpyruvylshikimate 3-phosphate synthase enzyme EPSPS is used in the synthesis of the amino acids tryptophan, phenylalanine and tyrosine. They affect grasses and dicots alike. Glyphosate (Roundup) is a systemic EPSPS inhibitor but inactivated by soil contact.

• Synthetic auxin inaugurated the era of organic herbicides. They were discovered in the 1940s after a long study of the plant growth regulator auxin. Synthetic auxins mimic this plant hormone. They have several points of action on the cell membrane, and are effective in the control of dicot plants. 2,4-D is a synthetic auxin herbicide.

• Photosystem II inhibitors reduce electron flow from water to NADPH2+ at the photochemical step in photosynthesis. They bind to the Qb site on the D1 protein, and prevent quinone from binding to this site. Therefore, this group of compounds cause electrons to accumulate on chlorophyll molecules. As a consequence, oxidation reactions in excess of those normally tolerated by the cell occur, and the plant dies. The triazine herbicides (including atrazine) and urea derivatives (diuron) are photosystem II inhibitors.

Organic Herbicides

Almost all herbicides in use today are considered "organic" herbicides in that they contain carbon as a primary molecular component. A notable exception would be the arsenical class of herbicides. Sometimes they are referred to as synthetic organic herbicides. Recently the term "organic" has come to imply products used in organic farming. Under this definition an organic herbicide is one that can be used in a farming enterprise that has been classified as organic. Organic herbicides are expensive and may not be affordable for commercial production. They are much less effective than synthetic herbicides and are generally used along with cultural and mechanical weed control practices.

Organic herbicides include:

• Spices are now effectively used in patented herbicides.

• Vinegar is effective for 5-20% solutions of acetic acid with higher concentrations most effective but mainly destroys surface growth and so respraying to treat regrowth is needed. Resistant plants generally succumb when weakened by respraying.

• Steam has been applied commercially but is now considered uneconomic and inadequate. It kills surface growth but not underground growth and so respraying to treat regrowth of perennials is needed.

• Flame is considered more effective than steam but suffers from the same difficulties.

• D-limonene (citrus oil), which is the active ingredient in Nature's Avenger Organic Herbicide. D-limonene (citrus oil) is a natural degreasing agent that strips the waxy skin or cuticle from weeds, causing dehydration and ultimately death. Environmentally safe, Nature’s Avenger Organic Herbicide is registered by the EPA - (U.S. Environmental Protection Agency), and approved for use in organic production by the USDA - (United States Department of Agriculture) and is OMRI - Organic Materials Review Institute listed.

Application

Most herbicides are applied as water-based sprays using ground equipment. Ground equipment varies in design, but large areas can be sprayed using self-propelled sprayers equipped with a long boom, of 60 to 80 feet (20 to 25 m) with flat fan nozzles spaced about every 20 in (500 mm). Towed, handheld, and even horse-drawn sprayers are also used.

Synthetic organic herbicides can generally be applied aerially using helicopters or airplanes, and can be applied through irrigation systems (chemigation).

Terminology

• Control is the destruction of unwanted weeds, or the damage of them to the point where they are no longer competitive with the crop.
• Suppression is incomplete control still providing some economic benefit, such as reduced competition with the crop.
• Crop Safety, for selective herbicides, is the relative absence of damage or stress to the crop. Most selective herbicides cause some visible stress to crop plants.

Major herbicides in use today

• 2,4-D, a broadleaf herbicide in the phenoxy group used in turf and in no-till field crop production. Now mainly used in a blend with other herbicides that allow lower rates of herbicides to be used, it is the most widely used herbicide in the world, third most commonly used in the United States. It is an example of synthetic auxin (plant hormone).
• aminopyralid is a broadleaf herbicide in the pyridine group, used to control broadleaf weeds on grassland, such as docks, thistles and nettles. Notorious for its ability to persist in compost.
• atrazine, a triazine herbicide used in corn and sorghum for control of broadleaf weeds and grasses. Still used because of its low cost and because it works extrodinarily well on a broad spectrum of weeds common in the U.S. corn belt, Atrazine is commonly used with other herbicides to reduce the over-all rate of atrazine and to lower the for potential groundwater contamination, it is a photosystem II inhibitor.
• clopyralid is a broadleaf herbicide in the pyridine group, used mainly in turf, rangeland, and for control of noxious thistles. Notorious for its ability to persist in compost. It is another example of synthetic auxin.
• dicamba, a post-emergent broadleaf herbicide with some soil activity, used on turf and field corn. It is another example of a synthetic auxin.
• Glufosinate ammonium, a broad-spectrum contact herbicide and is used to control weeds after the crop emerges or for total vegetation control on land not used for cultivation.
• Fluroxypyr, a systemic, selective herbicide used for the control of broad-leaved weeds in small grain cereals, maize, pastures, range land and turf. It is a synthetic auxin. In cereal growing, fluroxypyr's key importance is control of cleavers, Galium aparine. Other key broad-leaved weeds are also controlled.
• Glyphosate, a systemic non-selective (it kills any type of plant) herbicide used in no-till burndown and for weed control in crops that are genetically modified to resist its effects. It is an example of an EPSPs inhibitor.
• Imazapyr a non-selective herbicide used for the control of a broad range of weeds including terrestrial annual and perennial grasses and broadleaved herbs, woody species, and riparian and emergent aquatic species.
• Imazapic, a selective herbicide for both the pre- and post-emergent control of some annual and perennial grasses and some broadleaf weeds. Imazapic kills plants by inhibiting the production of branched chain amino acids (valine, leucine, and isoleucine), which are necessary for protein synthesis and cell growth.
• Linuron is a non-selective herbicide used in the control of grasses and broadleaf weeds. It works by inhibiting photosynthesis.
• Metolachlor is a pre-emergent herbicide widely used for control of annual grasses in corn and sorghum; it has displaced some of the atrazine in these uses.
• Paraquat, a nonselective contact herbicide used for no-till burndown and in aerial destruction of marijuana and coca plantings. More acutely toxic to people than any other herbicide in widespread commercial use.
• Pendimethalin, a pre-emergent herbicide widely used to control annual grasses and some broadleaf weeds in a very wide range of crops, including corn, soybeans, wheat, cotton, many tree and vine crops, and many turfgrass species.
• picloram, a pyridine herbicide mainly used to control unwanted trees in pastures and edges of fields. It is another synthetic auxin.
• Triclopyr, a systemic, foliar herbicide in the pyridine group. It is used to control broadleaf weeds while leaving grasses and conifers unaffected.

Herbicides of historical interest

• 2,4,5-Trichlorophenoxyacetic acid (2,4,5-T) was a widely used broadleaf herbicide until being phased out starting in the late 1970s. While 2,4,5-T itself is of only moderate toxicity, the manufacturing process for 2,4,5-T contaminates this chemical with trace amounts of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD is extremely toxic to humans. With proper temperature control during production of 2,4,5-T, TCDD levels can be held to about .005 ppm. Before the TCDD risk was well understood, early production facilities lacked proper temperature controls. Individual batches tested later were found to have as much as 60 ppm of TCDD.

• 2,4,5-T was withdrawn from use in the USA in 1983, at a time of heightened public sensitivity about chemical hazards in the environment. Public concern about dioxins was high, and production and use of other (non-herbicide) chemicals potentially containing TCDD contamination was also withdrawn. These included pentachlorophenol (a wood preservative) and PCBs (mainly used as stabilizing agents in transformer oil). Some feel that the 2,4,5-T withdrawal was not based on sound science. 2,4,5-T has since largely been replaced by dicamba and triclopyr.

• Agent Orange was a herbicide blend used by the U.S. military in Vietnam between January 1965 and April 1970 as a defoliant. It was a 50/50 mixture of the n-butyl esters of 2,4,5-T and 2,4-D. Because of TCDD contamination in the 2,4,5-T component, it has been blamed for serious illnesses in many veterans and Vietnamese people who were exposed to it. However, research on populations exposed to its dioxin contaminant have been inconsistent and inconclusive. Agent Orange often had much higher levels of TCDD than 2,4,5-T used in the US. The name Agent Orange is derived from the orange color-coded stripe used by the Army on barrels containing the product. It is worth noting that there were other blends of synthetic auxins at the time of the Vietnam War whose containers were recognized by their colors, such as Agent Purple and Agent Pink.

Soil Contamination: Electrical Resistance Heating Remediation

Electrical resistance heating (ERH) is an intensive in situ environmental remediation method that uses the flow of alternating current electricity to heat soil and groundwater and evaporate contaminants. Electrical current is passed through a targeted soil volume between subsurface electrode elements. The resistance to electrical flow that exists in the soil causes the formation of heat; resulting in an increase in temperature until the boiling point of water at depth is reached. After reaching this temperature, further energy input causes a phase change, forming steam and removing volatile contaminants. ERH is typically more cost effective when used for treating contaminant source areas.

History

Three-phase heating (see Technology below) was originally created to enhance oil recovery. This design was patented in 1976 by Bill Pritchett of ARCO. The patent has expired and is now available for public use.

Six-phase heating (see Technology below) was created and patented for the US Department of Energy (DOE) in the 1980’s for use on DOE sites as well as commercial applications.

Technology

Electrical resistance heating is used by the environmental restoration industry for remediation of contaminated soil and groundwater. ERH consists of constructing electrodes in the ground, applying alternating current (AC) electricity to the electrodes and heating the subsurface to temperatures that promote the evaporation of contaminants. Volatilized contaminants are captured by a subsurface vapor recovery system and conveyed to the surface along with recovered air and steam. Similar to Soil vapor extraction, the air, steam and volatilized contaminants are then treated at the surface to separate water, air and the contaminants. Treatment of the various streams depends on local regulations and the amount of contaminant.

Some low volatility organic contaminants have a short hydrolysis half life. For contaminants like these, i.e. 1,1,2,2–Tetrachloroethane and 1,1,1-Trichloroethane , hydrolysis can be the primary form of remediation. As the subsurface is heated the hydrolysis half life of the contaminant will decrease as described by the Arrhenius equation. This results in a rapid degradation of the contaminant. The hydrolysis by-product may be remediated by conventional ERH, however the majority of the mass of the primary contaminant will not be recovered but rather will degrade to a by-product.

There are predominantly two electrical load arrangements for ERH: three-phase and six-phase. Three-phase heating consists of electrodes in a repeating triangular or delta pattern. Adjacent electrodes are of a different electrical phase so electricity conducts between them as shown in Figure 1. The contaminated area is depicted by the green shape while the electrodes are depicted by the numbered circles.

Six-phase heating consists of six electrodes in a hexagonal pattern with a neutral electrode in the center of the array. The six-phase arrays are outlined in blue in Figure 2 below. Once again the contaminated area is depicted by the green shape while the electrodes are depicted by the numbered circles. In a six-phase heating pattern there can be hot spots and cold spots depending on the phases that are next to each other. For this reason, six-phase heating typically works best on small circular areas that are less than 65 feet in diameter.

ERH is typically most effective on volatile organic compounds (VOCs). The chlorinated compounds perchloroethylene, trichloroethylene, and cis or trans 1,2-dichloroethylene are contaminants that are easily remediated with ERH. The table shows contaminants that can be remediated with ERH along with their respective boiling points. Less volatile contaminants like xylene or diesel can also be remediated with ERH but energy requirements increase as the volatility decreases.

List of compounds that can be remediated with ERH
Chemical	Molecular Weight (g)	Boiling Point (°C)
1,1,1-trichloroethane	133.4	74
1,1,2-trichloroethane	133.4	114
1,1-dichloroethane	99	57
1,1-dichloroethene	97	32
1,2-dichloroethane	99	84
1,2-dichloropropane	167.9	97
benzene	78.1	80
carbon tetrachloride	153.8	77
chlorobenzene	112.6	132
chlorform	119.4	62
cis 1,2-dichloroethyene	97	60
dibromoethane	187.9	132
ethylbenzene	106.2	136
trichloro-trifluoroethane	187.4	48
gasoline	100	100
methylene chloride/dichloromethane	84.9	41
4-methyl-2-pentanone/methyl isobutyl ketone	100.2	117
2-methoxy-2-methylpropane/methyl tert butyl ether	88.1	55
perchloroethylene	165.8	121
trichloroethene	131.5	87
tert butyl alcohol	74.1	83
touene	92.1	111
trans 1,2-dichloroethene	97	48
vinyl chloride	62.5	-14
xylene	106.2	140

Electrode spacing and operating time can be adjusted to balance the overall remediation cost with the desired cleanup time. A typical remediation may consist of electrodes spaced 15 to 20 feet apart with operating times usually less than a year. The design and cost of an ERH remediation system depends on a number of factors, primarily the volume of soil/groundwater to be treated, the type of contamination, and the treatment goals. The physical and chemical properties of the target compounds are governed by laws that make heated remediations advantageous over most conventional methods. The electrical energy usage required for heating the subsurface and volatilizing the contaminants can account for 5 to 40% of the overall remediation cost.

There are several laws that govern an ERH remediation. Dalton’s law governs the boiling point of a relatively insoluble contaminant. Raoult’s law governs the boiling point of mutually soluble co-contaminants and Henry’s law governs the ratio of the contaminant in the vapor phase to the contaminant in the liquid phase.

Dalton's Law

For mutually insoluble compounds Dalton’s Law states that the partial pressure of a non aqueous phase liquid (NAPL) is equal to its vapor pressure, and that the NAPL in contact with water will boil when the vapor pressure of water plus the vapor pressure of the VOC is equal to ambient pressure. When a VOC-steam bubble is formed the composition of the bubble is proportional to the composite’s respective vapor pressures.

Raoult's Law

For mutually soluble compounds, Raoult’s Law states that the partial pressure of a compound is equal to its vapor pressure times its mole fraction. This means that mutually soluble contaminants will volatilize slower than if there was only one compound present.

Henry's Law

Henry’s law describes the tendency of a compound to join air in the vapor phase or dissolve in water. The Henry’s Law constant, sometimes called coefficient, is specific to each compound, varies with temperature, and predicts the amount of contaminant that will stay in the vapor phase or transfer to the liquid phase when exiting the condenser.

Weaknesses

• Weaknesses of ERH include heat losses on small sites. Treatment volumes that have a large surface area but are thin with respect to depth will have significant heat losses which makes ERH less efficient. The minimum treatment interval for efficient ERH remediation is approximately 10 vertical feet.

• Co-contaminants like oil or grease make remediation more difficult. Oil and grease cause a Raoult’s Law effect which requires more energy to remove the contaminants.

• Peat or high organic carbon in the subsurface will preferentially adsorb VOCs due to van der Waals forces. This preferential adsorption will increase the amount of energy required to remove the VOCs from the subsurface.

• Fuel sites are less-commonly treated by ERH because other less-expensive remediation technologies are available and because fuel sites are usually thin (resulting in significant heat losses).

• Sites within landfills are also challenging because metallic debris can distort the electrical current paths. ERH is more uniform in natural soil or rock.

Strengths

• ERH is adaptable to all soil types and sedimentary bedrock. ERH is also effective in both the vadose and saturated zones. Certain lithologies can limit traditional methods of remediation by preventing a reliable removal/destruction pathway for the contamination of concern. Because electricity can and does travel through any lithology that contains some water, ERH can be effective in any soil type. By forming buoyant steam bubbles during the heating process, ERH creates a carrier gas that transports the contamination of concern up and out of any soil type. ERH is not capable of desiccating the subsurface. In order for the subsurface to conduct electricity, there must be water present in the subsurface. Conductivity will cease before the subsurface is desiccated.

• ERH is commonly applied under active buildings or manufacturing facilities. Electrodes can be installed above grade within a fenced area or below grade to allow for unrestricted surface access to the treatment area.

• Although principally used for contaminant source areas, ERH can be used to achieve low remedial goals such as maximum contaminant levels, MCLs, for drinking water.

• After ERH treatment, elevated subsurface temperatures will slowly cool over a period of months or years and return to ambient. This period with elevated temperatures is an important part of the remediation process. The elevated temperatures will enhance Bioremediation, hydrolysis and iron reductive dehalogenation.

Soil Contamination: Bioremediation

Bioremediation can be defined as any process that uses microorganisms, fungi, green plants or their enzymes to return the natural environment altered by contaminants to its original condition. Bioremediation may be employed to attack specific soil contaminants, such as degradation of chlorinated hydrocarbons by bacteria. An example of a more general approach is the cleanup of oil spills by the addition of nitrate and/or sulfate fertilizers to facilitate the decomposition of crude oil by indigenous or exogenous bacteria.

Overview and applications

Naturally occurring bioremediation and phytoremediation have been used for centuries. For example, desalination of agricultural land by phytoextraction has a long tradition. Bioremediation technology using microorganisms was reportedly invented by George M. Robinson. He was the assistant county petroleum engineer for Santa Maria, California. During the 1960's, he spent his spare time experimenting with dirty jars and various mixes of microbes

Bio remediation technologies can be generally classified as in situ or ex situ. In situ bio remediation involves treating the contaminated material at the site while ex situ involves the removal of the contaminated material to be treated elsewhere. Some examples of bio remediation technologies are bio venting, land farming, bio reactor, composting, bio augmentation, rhizofiltration, and bio stimulation.

Not all contaminants, however, are easily treated by bioremediation using microorganisms. For example, heavy metals such as cadmium and lead are not readily absorbed or captured by organisms. The assimilation of metals such as mercury into the food chain may worsen matters. Phytoremediation is useful in these circumstances, because natural plants or transgenic plants are able to bio accumulate these toxins in their above-ground parts, which are then harvested for removal. The heavy metals in the harvested biomass may be further concentrated by incineration or even recycled for industrial use.

The elimination of a wide range of pollutants and wastes from the environment is an absolute require increasing our understanding of the relative importance of different pathways and regulatory networks to carbon flux in particular environments and for particular compounds and they will certainly accelerate the development of bioremediation technologies and bio transformation processes.

Genetic engineering approaches

The use of genetic engineering to create organisms specifically designed for bioremediation has great potential. The bacterium Deinococcus radiodurans (the most radioresistant organism known) has been modified to consume and digest toluene and ionic mercury from highly radioactive nuclear waste.

Mycoremediation

Mycoremediation is a form of bioremediation, the process of using mushrooms to return an environment (usually soil) contaminated by pollutants to a less contaminated state. The term mycoremediation was coined by Paul Stamets and refers specifically to the use of fungal mycelia in bio remediation.

One of the primary roles of fungi in the ecosystem is decomposition, which is performed by the mycelium. The mycelium secretes extracellular enzymes and acids that break down lignin and cellulose, the two main building blocks of plant fiber. These are organic compounds composed of long chains of carbon and hydrogen, structurally similar to many organic pollutants. The key to mycoremediation is determining the right fungal species to target a specific pollutant. Certain strains have been reported to successfully degrade the nerve gases VX and sarin.

In an experiment conducted in conjunction with Thomas, a major contributor in the bioremediation industry, a plot of soil contaminated with diesel oil was inoculated with mycelia of oyster mushrooms; traditional bioremediation techniques (bacteria) were used on control plots. After four weeks, more than 95% of many of the PAH (polycyclic aromatic hydrocarbons) had been reduced to non-toxic components in the mycelial-inoculated plots. It appears that the natural microbial community participates with the fungi to break down contaminants, eventually into carbon dioxide and water. Wood-degrading fungi are particularly effective in breaking down aromatic pollutants (toxic components of petroleum), as well as chlorinated compounds (certain persistent pesticides; Battelle, 2000).

Mycofiltration is a similar or same process, using fungal mycelia to filter toxic waste and microorganisms from water in soil.

Advantages

There are a number of cost/efficiency advantages to bioremediation, which can be employed in areas that are inaccessible without excavation. For example, hydrocarbon spills (specifically, petrol spills) or certain chlorinated solvents may contaminate groundwater, and introducing the appropriate electron acceptor or electron donor amendment, as appropriate, may significantly reduce contaminant concentrations after a lag time allowing for acclimation. This is typically much less expensive than excavation followed by disposal elsewhere, incineration or other ex situ treatment strategies, and reduces or eliminates the need for "pump and treat", a common practice at sites where hydrocarbons have contaminated clean groundwater.

Monitoring bioremediation

The process of bioremediation can be monitored indirectly by measuring the Oxidation Reduction Potential or redox in soil and groundwater, together with pH, temperature, oxygen content, electron acceptor/donor concentrations, and concentration of breakdown products (e.g. carbon dioxide). This table shows the (decreasing) biological breakdown rate as function of the redox potential.

Process	Reaction	Redox potential (Eh in mV)
aerobic:	O2 + 4e− + 4H+ → 2H2O	600 ~ 400
anaerobic:
denitrification	2NO3− + 10e− + 12H+ → N2 + 6H2O	500 ~ 200
manganese IV reduction	MnO2 + 2e− + 4H+ → Mn2+ + 2H2O	400 ~ 200
iron III reduction	Fe(OH)3 + e− + 3H+ → Fe2+ + 3H2O	300 ~ 100
sulfate reduction	SO42− + 8e− +10 H+ → H2S + 4H2O	0 ~ −150
fermentation	2CH2O → CO2 + CH4	−150 ~ −220

This, by itself and at a single site, gives little information about the process of remediation.

1. it is necessary to sample enough points on and around the contaminated site to be able to determine contours of equal redox potential. Contouring is usually done using specialised software, e.g. using Kriging interpolation.
2. if all the measurements of redox potential show that electron acceptors have been used up, it's in effect an indicator for total microbial activity. Chemical analysis is also required to determine when the levels of contaminants and their breakdown products have been reduced to below regulatory limits.
   

Water Quality

Water quality is the physical, chemical and biological characteristics of water in relationship to a set of standards. In the United States, Water Quality Standards are created by state agencies for different types of water bodies and water body locations per desired uses. The primary uses considered for such characterization are parameters which relate to drinking water, safety of human contact, and for health of ecosystems. The methods of hydrometry are used to quantify water characteristics.

In the setting of standards, agencies make political and technical/scientific decisions about how the water will be used. In the case of natural water bodies, they also make some reasonable estimate of pristine conditions. Different uses raise different concerns and therefore different standards are considered. Natural water bodies will vary in response to environmental conditions. Environmental scientists are working to understand the functioning of these systems, which determines sources and fates of contaminants. Environmental lawyers and policy makers are working to define water laws that designate the fore mentioned uses and natural conditions.

The vast majority of surface water on the planet is neither potable nor toxic. This remains true even if sea water in the oceans (which is too salty to drink) isn't counted. Another general perception of water quality is that of a simple property that tells whether water is polluted or not. In fact, water quality is a very complex subject, in part because water is a complex medium intrinsically tied to the ecology of the Earth. Industrial pollution is a major cause of water pollution, as well as runoff from agricultural areas, urban stormwater runoff and discharge of untreated sewage (especially in developing countries).

Categories

The parameters for water quality are determined by the intended use. Work in the area of water quality tends to be focused on water that is treated for human consumption or in the environment.

Human Consumption

Contaminants that may be in untreated water include microorganisms such as viruses and bacteria; inorganic contaminants such as salts and metals; pesticides and herbicides; organic chemical contaminants from industrial processes and petroleum use; and radioactive contaminants. Water quality depends on the local geology and ecosystem, as well as human uses such as sewage dispersion, industrial pollution, use of water bodies as a heat sink, and overuse (which may lower the level of the water).

In the United States, the U.S. Environmental Protection Agency (EPA) limits the amounts of certain contaminants in tap water provided by public water systems. The Safe Drinking Water Act authorizes EPA to issue two types of standards: primary standards regulate substances that potentially affect human health, and secondary standards prescribe aesthetic qualities, those that affect taste, odor, or appearance. The U.S. Food and Drug Administration (FDA) regulations establish limits for contaminants in bottled water that must provide the same protection for public health. Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of these contaminants does not necessarily indicate that the water poses a health risk.

Some people use water purification technology to remove contaminants from the municipal water supply they get in their homes, or from local pumps or bodies of water. For people who get water from a local stream, lake, or aquifer (well), their drinking water is not filtered by the local government.

Environmental Water Quality

Environmental water quality, also called ambient water quality, pertains to water bodies such as lakes, rivers, and oceans. Ambient water quality standards vary significantly due to different environmental conditions, ecosystems, and intended human uses. Toxic substances and high populations of certain microorganisms can present a health hazard for non-drinking purposes such as irrigation, swimming, fishing, rafting, boating, and industrial uses. These conditions may also affect wildlife which use the water for drinking or as a habitat. Modern water quality laws general specify protection of fishable/swimmable use and antidegradation of current conditions.

There is some desire among the public to return water bodies to pristine, or pre-industrial conditions. Current environmental laws focus of the designation of uses and therefore allow for some water contamination as long as the particular type of contamination is not harmful to the designated uses. Given the landscape changes in the watersheds of many freshwater bodies, returning to pristine conditions would be a significant challenge. In these cases, environmental scientists focus on achieving goals for maintaining populations of endangered species and protecting human health.

Measurement

The complexity of water quality as a subject is reflected in the many types of measurements of water quality indicators. Some of the simple measurements listed below can be made on-site (temperature, pH, dissolved oxygen, conductivity), in direct contact with the water source in question. More complex measurements that must be made in a lab setting require a water sample to be collected, preserved, and analyzed at another location. Making these complex measurements can be expensive. Because direct measurements of water quality can be expensive, ongoing monitoring programs are typically conducted by government agencies. However, there are local volunteer programs and resources available for some general assessment. Tools available to the general public are on-site test kits commonly used for home fish tanks and biological assessments.

The following is a list of indicators often measured by situational category:

Drinking Water

---

• Alkalinity
• Color of water
• pH
• Taste and odor (geosmin, 2-methylisoborneol (MIB), etc)
• Dissolved metals and salts (sodium, chloride, potassium, calcium, manganese, magnesium)
• Microorganisms such as fecal coliform bacteria (Escherichia coli), Cryptosporidium, and Giardia lamblia
• Dissolved metals and metalloids (lead, mercury, arsenic, etc.)
• Dissolved organics: colored dissolved organic matter (CDOM), dissolved organic carbon (DOC)
• Radon
• Heavy metals
• Pharmaceuticals
• Hormone analogs

Environmental

---

Chemical Assessment

• pH
• Conductivity (also see salinity)
• Dissolved Oxygen (DO)
• nitrate-N
• orthophosphates
• Chemical oxygen demand (COD)
• Biochemical oxygen demand (BOD)
• Pesticides

Physical Assessment

• Temperature
• Total suspended solids (TSS)
• Turbidity

Biological Assessment

Biological monitoring metrics have been developed in many places, and one widely used measure is the presence and abundance of members of the insect orders Ephemeroptera, Plecoptera and Trichoptera. (Common names are, respectively, Mayfly, Stonefly and Caddisfly.) EPT indexes will naturally vary from region to region, but generally, within a region, the greater the number of taxa from these orders, the better the water quality. EPA and other organizations in the United States offer guidance on developing a monitoring program and identifying members of these and other aquatic insect orders.

Individuals interested in monitoring water quality who cannot afford or manage lab scale analysis can also use biological indicators to get a general reading of water quality. One example is the IOWATER volunteer water monitoring program, which includes a benthic macroinvertebrate indicator key.

Standards & Reports

United States

In the United States each governing jurisdiction (states, territories, and covered tribal entities) is required to submit a set of biennial reports on the quality of water in their area. These reports submitted to, and approved by, EPA are known as the 303(d), 305(b) and 314 reports. These reports are completed by the governing jurisdiction, typically a Department of Environmental Quality or similar state agency, and are available on the web. In coming years it is expected that the governing jurisdictions will submit all three reports as a single document, called the "Integrated Report." The 305(b) report (National Water Quality Inventory Report to Congress) is a general report on water quality, providing overall information about the number of miles of streams and rivers and their aggregate condition. The 314 report has provided similar information for lakes. Under the Clean Water Act, states are required to adopt water quality standards for each of the possible designated uses that they assign to their waters. Should evidence suggest or document that a stream, river or lake has failed to meet the water quality criteria for one or more of its designated uses, it is placed on the 303(d) list of impaired waters. Once on the 303(d) list states are required to develop management plans establishing Total Maximum Daily Loads for the pollutant impairing the use of the water. These TMDLs establish the reductions needed to fully support the designated uses.

Wastewater

Waste water is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations. In the most common usage, it refers to the municipal waste water that contains a broad spectrum of contaminants resulting from the mixing of waste waters from different sources.

Sewage is correctly the subset of waste water that is contaminated with feces or urine, but is often used to mean any waste water. "Sewage" includes domestic, municipal, or industrial liquid waste products disposed of, usually via a pipe or sewer or similar structure, sometimes in a cesspool emptier.

The physical infrastructure, including pipes, pumps, screens, channels etc. used to convey sewage from its origin to the point of eventual treatment or disposal is termed sewerage.

Wastewater origin

Wastewater or sewage can come from(text in brackets indicates likely inclusions or contaminants) :-

• Human waste, usually from lavatories: (feces, used toilet paper, wipes, urine, other bodily fluids) also known as black water
• Cesspit leakage
• Septic tank discharge
• Sewage treatment plant discharge
• Washing water (personal, clothes, floors, dishes, etc.) also known as greywater or sullage
• Rainfall collected on roofs, yards, hard-standings, etc. (traces of oils and fuel but generally clean)
• Groundwater infiltrated into sewerage.
• Surplus manufactured liquids from domestic sources (drinks, cooking oil, pesticides, lubricating oil, paint, cleaning liquids, etc.)
• Urban rainfall run-off from roads, car-parks, roofs, side-walks or pavements (contains oils, animal feces, litter, fuel residues, rubber residues, metals from vehicle exhausts etc)
• Seawater ingress (salt, micro-biota, high volumes)
• Direct ingress of river water (micro-biota, high volumes)
• Direct ingress of man-made liquids (illegal disposal of pesticides, used oils, etc.)
• Highway drainage (oil, de-icing agents, rubber residues)
• Storm drains (almost anything including cars, shopping trolleys, trees, cattle etc.)
• Black water - surface water contaminated by sewage
• Industrial waste:-
• industrial site drainage (silt, sand, alkali, oil, chemical)
  • Industrial cooling waters (biocides, heat, slimes, silt)
  • Industrial process waters
  • Organic - bio-degradable - includes waste from abattoirs and creameries and ice-cream manufacture.
  • Organic - non bio-degradable or difficult to treat - for example Pharmaceutical or Pesticide manufacturing
  • Inorganic - for example from the metalworking industry
  • extreme pH - from acid/alkali manufacturing, metal plating
  • Toxic - e.g. from metal plating, cyanide production, pesticide manufacturing
  • Solids and Emulsions - e.g. Paper manufacturing, food stuffs, lubricating and hydraulic oil manufacture
  • agricultural drainage - direct and diffuse

Wastewater constituents

The composition of wastewater varies widely. This is a partial list of what it may contain:

• Water ( > 95%) which is often added during flushing to carry the waste down a drain
• Pathogens such as bacteria, viruses, prions and parasitic worms.
• Non-pathogenic bacteria (> 100,000 / ml for sewage)
• Organic particles such as faeces, hairs, food, vomit, paper fibers, plant material, humus, etc.
• Soluble organic material such as urea, fruit sugars, soluble proteins, drugs, pharmaceuticals, etc.
• Inorganic particles such as sand, grit, metal particles, ceramics, etc.
• Soluble inorganic material such as ammonia, road-salt, sea-salt, cyanide, hydrogen sulfide, thiocyanates, thiosulfates, etc.
• Animals such as protozoa, insects, arthropods, small fish, etc.
• Macro-solids such as sanitary napkins, nappies/diapers, condoms, needles, children's toys, dead pets, body parts, etc.
• Gases such as hydrogen sulfide, carbon dioxide, methane, etc.
• Emulsions such as paints, adhesives, mayonnaise, hair colorants, emulsified oils, etc.
• Toxins such as pesticides, poisons, herbicides, etc.

Wastewater quality indicators

Any oxidizable material present in a natural waterway or in an industrial waste water will be oxidized both by biochemical (bacterial) or chemical processes. The result is that the oxygen content of the water will be decreased. Basically, the reaction for biochemical oxidation may be written as:

Oxidizable material + bacteria + nutrient + O₂ → CO₂ + H₂O + oxidized inorganics such as NO₃ or SO₄

Oxygen consumption by reducing chemicals such as sulfides and nitrites is typified as follows:

S^-- + 2 O₂ → SO₄^--

NO₂^- + ½ O₂ → NO₃^-

Since all natural waterways contain bacteria and nutrient, almost any waste compounds introduced into such waterways will initiate biochemical reactions (such as shown above). Those biochemical reactions create what is measured in the laboratory as the Biochemical oxygen demand (BOD).

Oxidizable chemicals (such as reducing chemicals) introduced into a natural water will similarly initiate chemical reactions (such as shown above). Those chemical reactions create what is measured in the laboratory as the Chemical oxygen demand (COD).

Both the BOD and COD tests are a measure of the relative oxygen-depletion effect of a waste contaminant. Both have been widely adopted as a measure of pollution effect. The BOD test measures the oxygen demand of biodegradable pollutants whereas the COD test measures the oxygen demand of bio gradable pollutants plus the oxygen demand of non-biodegradable oxidizable pollutants.

The so-called 5-day BOD measures the amount of oxygen consumed by biochemical oxidation of waste contaminants in a 5-day period. The total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion is called the Ultimate BOD. The Ultimate BOD is too time consuming, so the 5-day BOD has almost universally been adopted as a measure of relative pollution effect.

There are also many different COD tests. Perhaps, the most common is the 4-hour COD.

It should be emphasized that there is no generalized correlation between the 5-day BOD and the Ultimate BOD. Likewise, there is no generalized correlation between BOD and COD. It is possible to develop such correlations for a specific waste contaminant in a specific waste water stream ... but such correlations cannot be generalized for use with any other waste contaminants or waste water streams.

The laboratory test procedures for the determining the above oxygen demands are detailed in the following sections of the "Standard Methods For the Examination Of Water and Waste water" available at www.standardmethods.org:

• 5-day BOD and Ultimate BOD: Sections 5210B and 5210C
• COD: Section 5220

Sewage disposal

In some urban areas, sewage is carried separately in sanitary sewers and runoff from streets is carried in storm drains. Access to either of these is typically through a manhole. During high precipitation periods a sanitary sewer overflow can occur, causing potential public health and ecological damage.

Sewage may drain directly into major watersheds with minimal or no treatment. When untreated, sewage can have serious impacts on the quality of an environment and on the health of people. Pathogens can cause a variety of illnesses. Some chemicals pose risks even at very low concentrations and can remain a threat for long periods of time because of bio accumulation in animal or human tissue.

Treatment

There are numerous processes that can be used to clean up waste waters depending on the type and extent of contamination. Most waste water is treated in industrial-scale waste water treatment plants (WWTPs) which may include physical, chemical and biological treatment processes. However, the use of septic tanks and other On-Site Sewage Facilities (OSSF) is widespread in rural areas, serving up to one quarter of the homes in the U.S. The most important aerobic treatment system is the activated sludge process, based on the maintenance and recirculation of a complex biomass composed by micro-organisms able to absorb and adsorb the organic matter carried in the waste water. Anaerobic processes are widely applied in the treatment of industrial waste waters and biological sludge. Some waste water may be highly treated and reused as reclaimed water. For some waste waters ecological approaches using reed bed systems such as constructed wetlands may be appropriate. Modern systems include tertiary treatment by micro filtration or synthetic membranes. After membrane filtration, the treated waste water is indistinguishable from waters of natural origin of drinking quality. Nitrates can be removed from waste water by microbial denitrification, for which a small amount of methanol is typically added to provide the bacteria with a source of carbon. Ozone Waste Water Treatment is also growing in popularity, and requires the use of an ozone generator, which decontaminates the water as Ozone bubbles percolate through the tank.

Disposal of waste waters from an industrial plant is a difficult and costly problem. Most petroleum refineries, chemical and petrochemical plants have onsite facilities to treat their waste waters so that the pollutant concentrations in the treated waste water comply with the local and/or national regulations regarding disposal of waste waters into community treatment plants or into rivers, lakes or oceans.

Reuse

Treated waste water can be reused as drinking water, in industry (cooling towers), in artificial recharge of aquifers, in agriculture (70% of Israel's irrigated agriculture is based on highly purified waste water) and in the rehabilitation of natural ecosystems (Florida's Everglades).

Algal fuel

Woods Hole Oceanographic Institution and Harbor Branch Oceanographic Institution, following the conclusions of the USDOE´s Aquatic Species Program, use waste water for breeding algae. The waste water from domestic and industrial sources contain rich organic compounds, which accelerate the growth of algae. This algae can be used to produce algal fuels.

Algae wheel, based in Indianapolis, Indiana, presented a proposal to build a new waste water treatment facility in Cedar Lake, Indiana that uses algae to treat municipal waste water and uses the sludge byproduct to produce bio fuel.

Thermal Pollution

Thermal pollution is a rise or fall in the temperature change in a natural body of water caused by human influence. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. When water used as a coolant is returned to the natural environment at a higher temperature the change in temperature impacts organisms by (a) decreasing oxygen supply, and (b) affecting ecosystem composition. Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers. This affects fish (particularly eggs and larvae), macroinvertebrates and river productivity.

Ecological effects — warm water

Warm water typically decreases the level of dissolved oxygen in the water. The decrease in levels of dissolved oxygen can harm aquatic animals such as fish, amphibians and copepods. Thermal pollution may also increase the metabolic rate of aquatic animals, as enzyme activity, resulting in these organisms consuming more food in a shorter time than if their environment were not changed. An increased metabolic rate may result in food source shortages, causing a sharp decrease in a population. Changes in the environment may also result in a migration of organisms to another, more suitable environment, and to in-migration of fishes that normally only live in warmer waters elsewhere. This leads to competition for fewer resources; the more adapted organisms moving in may have an advantage over organisms that are not used to the warmer temperature. As a result one has the problem of compromising food chains of the old and new environments. Biodiversity can be decreased as a result.

It is known that temperature changes of even one to two degrees Celsius can cause significant changes in organism metabolism and other adverse cellular biology effects. Principal adverse changes can include rendering cell walls less permeable to necessary osmosis, coagulation of cell proteins, and alteration of enzyme metabolism. These cellular level effects can adversely affect mortality and reproduction.

Primary producers are affected by warm water because higher water temperature increases plant growth rates, resulting in a shorter lifespan and species overpopulation. This can cause an algae bloom which reduces the oxygen levels in the water. The higher plant density leads to an increased plant respiration rate because the reduced light intensity decreases photosynthesis. This is similar to the eutrophication that occurs when watercourses are polluted with leached agricultural inorganic fertilizers.

A large increase in temperature can lead to the denaturing of life-supporting enzymes by breaking down hydrogen- and disulphide bonds within the quaternary structure of the enzymes. Decreased enzyme activity in aquatic organisms can cause problems such as the inability to break down lipids, which leads to malnutrition.

In limited cases, warm water has little deleterious effect and may even lead to improved function of the receiving aquatic ecosystem. This phenomenon is seen especially in seasonal waters and is known as thermal enrichment. An extreme case is derived from the aggregational habits of the manatee, which often uses power plant discharge sites during winter. Projections suggest that manatee populations would decline upon the removal of these discharges.

The added heat lowers the dissolved oxygen content and may cause serious problems for the plants and animals living there. In extreme cases, major fish kills can result. Warm water may also increase the metabolic rate of aquatic animals, as enzyme activity, meaning that these organisms will consume more food in a shorter time than if their environment was not changed. The temperature can be as high as 70 degrees Fahrenheit for freshwater, 80 degrees Fahrenheit for saltwater, and 85 degrees Fahrenheit for tropical fish.

Ecological effects — cold water

Releases of unnaturally cold water from reservoirs can dramatically change the fish and macro invertebrate fauna of rivers, and reduce river productivity. In Australia, where many rivers have warmer temperature regimes, native fish species have been eliminated, and macro invertebrate faunas have been drastically altered and impoverished. The temperatures for freshwater fish can be as low as 50 degrees Fahrenheit, saltwater 75 degrees Fahrenheit, and Tropical 80 degrees Fahrenheit.

Computer modeling of thermal pollution

In the 1970s there was considerable activity from scientists in quantifying effects of thermal pollution. Hydrologists, physicists, meteorologists, and computer scientists combined their skills in one of the first interdisciplinary pursuits of the modern environmental science era. First came the application of gaussian function dispersal modeling that forecasts how a thermal plume is formed from a thermal point source and predicts the distribution of aquatic temperatures. The ultimate model was developed by the U.S. Environmental Protection Agency introducing the statistical variations in meteorology to predict the resulting plume from a thermal outfall.

Surface Runoff

Surface runoff is the water flow which occurs when soil is infiltrated to full capacity and excess water, from rain, snow melt, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source. If a non-point source contains man-made contaminants, the runoff is called nonpoint source pollution. A land area which produces runoff draining to common point is called a watershed. When runoff flows along the ground, it can pick up soil contaminants such as petroleum, pesticides (in particular herbicides and insecticides), or fertilizers that become discharge or non-point source pollution.

Generation

Surface runoff can be generated either by rainfall or by the melting of snow or glaciers.

Snow and glacier melt occur only in areas cold enough for these to form permanently. Typically snowmelt will peak in the spring and glacier melt in the summer, leading to pronounced flow maxima in rivers affected by them. The determining factor of the rate of melting of snow or glaciers is both air temperature and the duration of sunlight. In high mountain regions, streams frequently rise on sunny days and fall on cloudy ones for this reason.

In areas where there is no snow, runoff will come from rainfall. However, not all rainfall will produce runoff because storage from soils can absorb light showers. On the extremely ancient soils of Australia and Southern Africa, proteoid roots with their extremely dense networks of root hairs can absorb so much rainwater as to prevent runoff even when substantial amounts of rain fall. In these regions, even on relatively less infertile cracking clay soils, high amounts of rainfall and low potential evaporation are needed to generate any surface runoff, leading to specialised adaptations to extremely variable (usually ephemeral) streams.

Infiltration excess overland flow

This occurs when the rate of rainfall on a surface exceeds the rate at which water can infiltrate the ground, and any depression storage has already been filled. This is called infiltration excess overland flow, Hortonian overland flow (after Robert E. Horton), or unsaturated overland flow. This more commonly occurs in arid and semi-arid regions, where rainfall intensities are high and the soil infiltration capacity is reduced because of surface sealing, or in paved areas.

Saturation excess overland flow

When the soil is saturated and the depression storage filled, and rain continues to fall, the rainfall will immediately produce surface runoff. (Note in the photo to the left the microdepressions are full of water as seen in the lower left of the image.) The level of antecedent soil moisture is one factor affecting the time until soil becomes saturated. This runoff is saturation excess overland flow or saturated overland flow.

Subsurface return flow

After water infiltrates the soil on an up-slope portion of a hill, the water may flow laterally through the soil, and exfiltrate (flow out of the soil) closer to a channel. This is called subsurface return flow or interflow.

As it flows, the amount of runoff may be reduced in a number of possible ways: a small portion of it may evapotranspire; water may become temporarily stored in microtopographic depressions; and a portion of it may become run-on, which is the infiltration of runoff as it flows overland. Any remaining surface water eventually flows into a receiving water body such as a river, lake, estuary or ocean.

Human impact on surface runoff

Urbanization increases surface runoff, by creating more impervious surfaces such as pavement and buildings, that do not allow percolation of the water down through the soil to the aquifer. It is instead forced directly into streams or storm water runoff drains, where erosion and siltation can be major problems, even when flooding is not. Increased runoff reduces groundwater recharge, thus lowering the water table and making droughts worse, especially for farmers and others who depend on water wells.

When anthropogenic contaminants are dissolved or suspended in runoff, the human impact is expanded to create water pollution. This pollutant load can reach various receiving waters such as streams, rivers, lakes, estuaries and oceans with resultant water chemistry changes to these water systems and their related ecosystems.

A 2008 report by the United States National Research Council identified urban stormwater as a leading source of water quality problems in the U.S.

A contrarian could note there is considerable surface runoff in natural systems from animal wastes being entrained in runoff or from natural sediment loading in the absence of human alteration of the land. While these statements are true, they fail to convey that the most pernicious consequences to human health and ecosystems are from runoff issues related to human intervention; however, in underdeveloped countries the proportion of runoff attributable to natural factors has greater dominance, principally due to the lack of isolation of water supplies from potential animal waste carrying runoff.

Effects of surface runoff

Erosion

Surface runoff causes erosion of the earth's surface. There are four principal types of erosion: splash erosion, gully erosion, sheet erosion and stream bed erosion. Splash erosion is the result of mechanical collision of raindrops with the soil surface. Dislodged soil particles becoming suspended in the surface runoff and carried into streams and rivers. Gully erosion occurs when the power of runoff is strong enough that it cuts a well defined channel. These channels can be as small as one centimeter wide or as large as several meters. Sheet erosion is the overland transport of runoff without a well defined channel. In the case of gully erosion, large amounts of material can be transported in a small time period. Stream bed erosion is the attrition of stream banks or bottoms by rapidly flowing rivers or creeks.

Reduced crop productivity usually results from erosion, and these effects are studied in the field of soil conservation. The soil particles carried in runoff vary in size from about .001 millimeter to 1.0 millimeter in diameter. Larger particles settle over short transport distances, whereas small particles can be carried over long distances suspended in the water column. Erosion of silty soils that contain smaller particles generates turbidity and diminishes light transmission, which disrupts aquatic ecosystems.

Entire sections of countries have been rendered unproductive by erosion. On the high central plateau of Madagascar, approximately ten percent of that country's land area, virtually the entire landscape is devoid of vegetation, with erosive gully furrows typically in excess of 50 meters deep and one kilometer wide. Shifting cultivation is a farming system which sometimes incorporates the slash and burn method in some regions of the world. Erosion cause loss of the fertile top soil and reduces the its fertility and quality of the agricultural produce.

Modern industrial farming is another major cause of erosion. In some areas in the American corn belt more than 50 percent of the original topsoil has been carried away within the last 100 years.

Environmental impacts

The principal environmental issues associated with runoff are the impacts to surface water, groundwater and soil through transport of water pollutants to these systems. Ultimately these consequences translate into human health risk, ecosystem disturbance and aesthetic impact to water resources. Some of the contaminants that create the greatest impact to surface waters arising from runoff are petroleum substances, herbicides and fertilizers. Quantitative uptake by surface runoff of pesticides and other contaminants has been studied since the 1960s, and early on contact of pesticides with water was known to enhance phytotoxicity. In the case of surface waters, the impacts translate to water pollution, since the streams and rivers have received runoff carrying various chemicals or sediments. When surface waters are used as potable water supplies, they can be compromised regarding health risks and drinking water aesthetics (that is, odor, color and turbidity effects). Contaminated surface waters risk altering the metabolic processes of the aquatic species that they host; these alterations can lead to death, such as fish kills, or alter the balance of populations present. Other specific impacts are on animal mating, spawning, egg and larvae viability, juvenile survival and plant productivity. Some researches show surface runoff of pesticides, such as DDT, can alter the gender of fish species genetically, which transforms male into female fish.

In the case of groundwater, the main issue is contamination of drinking water, if the aquifer is abstracted for human use. Regarding soil contamination, runoff waters can have two important pathways of concern. Firstly, runoff water can extract soil contaminants and carry them in the form of water pollution to even more sensitive aquatic habitats. Secondly, runoff can deposit contaminants on relatively pristine soils, creating health or ecological consequences.

Flooding

Flooding occurs when a watercourse is unable to convey the quantity of runoff flowing downstream. The frequency with which this occurs is described by a return period. Flooding is a natural process, which maintains ecosystem composition and processes, but it can also be altered by land use changes such as river engineering. Floods can be both beneficial to societies or cause damage. Agriculture along the Nile floodplain took advantage of the seasonal flooding that deposited nutrients beneficial for crops. However, as the number and susceptibility of settlements increase, flooding increasingly becomes a natural hazard. Adverse impacts span loss of life, property damage, contamination of water supplies, loss of crops, and social dislocation and temporary homelessness. Floods are among the most devastating of natural disasters.

Agricultural issues

A common context of run-off deals with agriculture. When farmland is tilled and bare soil is revealed, rainwater carries billions of tons of topsoil into waterways each year, causing loss of valuable topsoil and adding sediment to produce turbidity in surface waters.

The other context of agricultural issues involves the transport of agricultural chemicals (nitrates, phosphates, pesticides, herbicides etc) via surface runoff. This result occurs when chemical use is excessive or poorly timed with respect to high precipitation. The resulting contaminated runoff represents not only a waste of agricultural chemicals, but also an environmental threat to downstream ecosystems. The alternative to conventional farming is organic farming which eliminates or greatly reduces chemical usage.

Measurement and mathematical modeling

Runoff is analyzed by using mathematical models in combination with various water quality sampling methods. Measurements can be made using continuous automated water quality analysis instruments targeted on pollutants such as specific organic or inorganic chemicals, pH, turbidity etc. or targeted on secondary indicators such as dissolved oxygen. Measurements can also be made in batch form by extracting a single water sample and conducting any number of chemical or physical tests on that sample.

In the 1950s or earlier hydrology transport models appeared to calculate quantities of runoff, primarily for flood forecasting. Beginning in the early 1970s computer models were developed to analyze the transport of runoff carrying water pollutants, which considered dissolution rates of various chemicals, infiltration into soils and ultimate pollutant load delivered to receiving waters. One of the earliest models addressing chemical dissolution in runoff and resulting transport was developed in the early 1970s under contract to the United States Environmental Protection Agency. This computer model formed the basis of much of the mitigation study that led to strategies for land use and chemical handling controls.

Other computer models have been developed (such as the DSSAM Model) that allow surface runoff to be tracked through a river course as reactive water pollutants. In this case the surface runoff may be considered to be a line source of water pollution to the receiving waters.

Mitigation and treatment

Mitigation of adverse impacts of runoff can take several forms:

• Land use development controls aimed at minimizing impervious surfaces in urban areas
• Erosion controls for farms and construction sites
• Flood control programs
• Chemical use and handling controls in agriculture, landscape maintenance, industrial use, etc.

Regarding Land use controls, the U.S. Environmental Protection Agency and others have encouraged research on methods of minimizing total surface runoff by avoiding unnecessary hardscape. Many municipalities have produced guidelines and codes for land developers that encourage minimum width sidewalks, use of pavers set in earth for driveways and walkways and other design techniques to allow maximum water infiltration in urban settings. An example land use control program can be viewed at seen in the city of Santa Monica, California.

Erosion controls have appeared since medieval times when farmers realized the importance of contour farming to protect soil resources. Beginning in the 1950s these agricultural methods became increasingly more sophisticated. In the 1960s some state and local governments began to focus their efforts on mitigation of construction runoff by requiring builders to implement erosion and sediment controls (ESCs). This included such techniques as: use of straw bales and barriers to slow runoff on slopes, installation of silt fences, programming construction for months that have less rainfall and minimizing extent and duration of exposed graded areas. Montgomery County, Maryland implemented the first local government sediment control program in 1965, and this was followed by a statewide program in Maryland in 1970.

Flood control programs as early as the first half of the twentieth century became quantitative in predicting peak flows of riverine systems. Progressively strategies have been developed to minimize peak flows and also to reduce channel velocities. Some of the techniques commonly applied are: provision of holding ponds to buffer riverine peak flows, use of energy dissipators in channels to reduce stream velocity and land use controls (above) to minimize runoff.

Chemical use and handling has become a focal point mainly since passage of NEPA in the U.S. States and cities have become more vigilant in controlling the containment and storage of toxic chemicals, thus preventing releases and leakage. Methods commonly applied are: requirements for double containment of underground storage tanks, registration of hazardous materials usage, reduction in numbers of allowed pesticides and more stringent regulation of fertilizers and herbicides in landscape maintenance. In many industrial cases, pretreatment of wastes is required, to minimize escape of pollutants into sanitary or storm water sewers.

The U.S. Clean Water Act (CWA) requires that local governments in urbanized areas (as defined by the Census Bureau) obtain storm water discharge permits for their drainage systems. Essentially this means that the locality must operate a storm water management program for all surface runoff that enters the municipal separate storm sewer system ("MS4"). EPA and state regulations and related publications outline six basic components that each local program must contain:

• Public education (informing individuals, households, businesses about ways to avoid stormwater pollution)
• Public involvement (support public participation in implementation of local programs)
• Illicit discharge detection & elimination (removing sanitary sewer or other non-stormwater connections to the MS4)
• Construction site runoff controls (i.e. erosion & sediment controls)
• Post-construction (i.e. permanent) storm water management controls
• Pollution prevention and "good housekeeping" measures (e.g. system maintenance).

Other property owners which operate storm drain systems similar to municipalities, such as state highway systems, universities, military bases and prisons, are also subject to the MS4 permit requirements.

Ship Pollution

Ship pollution is the pollution of air and water by shipping. It is a problem that has been accelerating as trade has become increasingly globalized, posing an increasing threat to the world’s oceans and waterways as globalization continues. It is expected that, “…shipping traffic to and from the USA is projected to double by 2020". Because of increased traffic in ocean ports, pollution from ships also directly affects coastal areas. The pollution produced affects biodiversity, climate, food, and human health. However, the degree to which humans are polluting and how it affects the world is highly debated and has been a hot international topic for the past 30 years.

Sources and causes of ship pollution

Ships can pollute the waterways and oceans in many ways. For instance, spills from oil tankers and chemical tankers, and ejection of sulfur dioxide, nitrogen dioxide and carbon dioxide gases into the atmosphere from exhaust fumes. Discharge of cargo residues from bulk carriers can pollute ports, waterways and oceans. Ships create noise pollution that disturbs natural wildlife, and water from ballast tanks can spread harmful algae and other invasive species. In many instances vessels due to a variety of reasons intentionally discharge illegal wastes despite foreign and domestic regulation prohibiting such actions.

This section describes how ships pollute the ocean; for the Protocol of 1978 Relating to the International Convention for the Prevention of Pollution From Ships of 1973, sometimes abbreviated as Ship Pollution, refer to MARPOL 73/78.

Ballast water

When a larger vessel, such as a container ship or an oil tanker unloads cargo, seawater is pumped into compartments in the hull. Similarly, when a larger vessel is being loaded it discharges seawater from these compartments. The sea water is meant to help stabilize and balance a ship. Ballast discharges from ships are responsible for tar balls in the open oceans and seas, and can cause problems navigating tanker routes. Nevertheless, the discharge of ballast water only accounts for a small percentage of oil pollution in the marine environment.

Ships are also responsible for transporting harmful organisms in their ballast water. Meinesz believes that one of the worst cases of a single invasive species causing harm to an ecosystem can be attributed to a seemingly harmless jellyfish. Mnemiopsis leidyi, a species of comb jellyfish that inhabits estuaries from the United States to the Valdés peninsula in Argentina along the Atlantic coast, has caused notable damage in the Black Sea. It was first introduced in 1982, and thought to have been transported to the Black Sea in a ship’s ballast water. The population of the jellyfish shot up exponentially and, by 1988, it was wreaking havoc upon the local fishing industry. “The anchovy catch fell from 204,000 tons in 1984 to 200 tons in 1993; sprat from 24,600 tons in 1984 to 12,000 tons in 1993; horse mackerel from 4,000 tons in 1984 to zero in 1993". Now that the jellyfish have exhausted the zoo plankton, including fish larvae, their numbers have fallen dramatically, yet they continue to maintain a stranglehold on the ecosystem. Recently the jellyfish have been discovered in the Caspian Sea. Invasive species can take over once occupied areas, facilitate the spread of new diseases, introduce new genetic material, alter landscapes and jeopardize the ability of native species to obtain food. “On land and in the sea, invasive species are responsible for about 137 billion dollars in lost revenue and management costs in the U.S. each year”.

In addition to introducing non native species into new environments, ballast and bilge discharge from ships can spread human pathogens and other harmful diseases and toxins potentially causing health issues for humans and marine life alike. Discharges into coastal waters along with other sources of marine pollution have the potential to be toxic to marine plants, animals, and microorganisms causing alterations such as changes in growth, disruption of hormone cycles, birth defects, suppression of the immune system, and disorders resulting in cancer, tumors, and genetic abnormalities or even death. They may also have the opposite affect upon some marine life stimulating growth and providing a source of food. Sources of seafood can become contaminated and unhealthy for consumption. Not surprisingly, cholera outbreaks have been attributed to ship operations. “Current research indicates that the bacterium responsible for causing cholera, Vibrio cholerae can spread through attachment to marine organisms in ship ballast water”. Shellfish and drinking water can then be contaminated when the ship discharges its ballast water.

Exhaust emissions

Exhaust emissions from ships are considered to be a significant source of air pollution. “Seagoing vessels are responsible for an estimated 14 percent of emissions of nitrogen from fossil fuels and 16 percent of the emissions of sulfur from petroleum uses into the atmosphere”. In Europe ships make up a large percentage of the sulfur introduced to the air, “…as much sulfur as all the cars, lorries and factories in Europe put together”. “By 2010, up to 40% of air pollution over land could come from ships”. Sulfur in the air creates acid rain which damages crops and buildings. When inhaled the sulfur is known to cause respiratory problems and even increase the risk of a heart attack. According to Irene Blooming, a spokeswoman for the European environmental coalition Seas at Risk, the fuel used in oil tankers and container ships is high in sulfur and cheaper to buy compared to the fuel used for domestic land use. “A ship lets out around 50 times more sulfur than a lorry per metric tonne of cargo carried”. Cities in the U.S. like Long Beach, Los Angeles, Houston, Galveston, and Pittsburgh see some of the heaviest shipping traffic in the nation and have left local officials desperately trying to clean up the air. Increasing trade between the U.S. and China is helping to increase the number of vessels navigating the Pacific and exacerbating many of the environmental problems. To maintain the level of growth China is currently experiencing, large amounts of grain are being shipped to China by the boat load. The number of voyages are expected to continue increasing.

Oil spills

Most commonly associated with ship pollution are oil spills. While less frequent than the pollution that occurs from daily operations, oil spills have devastating effects. While being toxic to marine life, polycyclic aromatic hydrocarbons (PAHs), the components in crude oil, are very difficult to clean up, and last for years in the sediment and marine environment. Marine species constantly exposed to PAHs can exhibit developmental problems, susceptibility to disease, and abnormal reproductive cycles. One of the more widely known spills was the Exxon Valdez incident in Alaska. The ship ran aground and dumped a massive amount of oil into the ocean in March 1989. Despite efforts of scientists, managers, and volunteers over 400,000 seabirds, about 1,000 sea otters, and immense numbers of fish were killed.

Cruise ships

Along with global trade the tourism industry has also seen growth in recent years. The cruise ship industry has seen 8 percent annual growth and continues to increase demand. With some cruise ships holding upwards of 5000 people, passengers and crew combined, these ships are likened to floating cities. “In one week, a typical cruise ship generates 210,000 gallons of black water (sewage), 1,000,000 gallons of gray water (shower, sink, dish washing water), 37,000 gallons of oily bilge water, more than eight tons of solid waste, millions of gallons of ballast water containing potential invasive species, and toxic wastes from dry cleaning and photo processing laboratories”. This is also compounded with fuel emissions to have detrimental effects on the environment. From 1993 to 1998, cruise ships were involved in 104 confirmed cases of illegal discharge of oil, garbage, and hazardous wastes. One of the worst reported cases was by Royal Caribbean Cruises Ltd. Over several years, while in U.S. waters, they had been routinely and deliberately dumping waste oil, photo processing, dry cleaning, and print shop chemicals into coastal waters. Their ships were even fitted with concealed piping that would bypass pollution treatment equipment.

Regulation

Some of the major international efforts in the form of treaties are the Marine Pollution Treaty, Honolulu, which deals with regulating marine pollution from ships, and the UN Convention on Law of the Sea, which deals with marine species and pollution. While plenty of local and international regulations have been introduced throughout maritime history, much of the current regulations are considered inadequate. “In general, the treaties tend to emphasize the technical features of safety and pollution control measures without going to the root causes of sub-standard shipping, the absence of incentives for compliance and the lack of enforceability of measures”. Cruise ships for example are exempt from regulation under the Clean Water Act of 1972 (CWA) point source permitting system that requires compliance with U.S. federal standards through technological requirements. In the Caribbean, many ports lack proper waste disposal facilities, and many ships dump their waste at sea.

Oil Spill

An oil spill is the release of a liquid petroleum hydrocarbon into the environment due to human activity, and is a form of pollution. The term often refers to marine oil spills, where oil is released into the ocean or coastal waters. The oil may be a variety of materials, including crude oil, refined petroleum products (such as gasoline or diesel fuel) or by-products, ships' bunkers, oily refuse or oil mixed in waste. Spills take months or even years to clean up.

Oil is also released into the environment from natural geologic seeps on the sea floor. Most human-made oil pollution comes from land-based activity, but public attention and regulation has tended to focus most sharply on seagoing oil tankers.

Environmental effects

The oil penetrates and opens up the structure of the plumage of birds, reducing its insulating ability, and so making the birds more vulnerable to temperature fluctuations and much less buoyant in the water. It also impairs birds' flight abilities, making it difficult or impossible to forage and escape from predators. As they attempt to preen, birds typically ingest oil that coats their feathers, causing kidney damage, altered liver function, and digestive tract irritation. This and the limited foraging ability quickly causes dehydration and metabolic imbalances. Hormonal balance alteration including changes in luteinizing protein can also result in some birds exposed to petroleum. Most birds affected by an oil spill die unless there is human intervention.

Marine mammals exposed to oil spills are affected in similar ways as seabirds. Oil coats the fur of Sea otters and seals, reducing its insulation abilities and leading to body temperature fluctuations and hypothermia. Ingestion of the oil causes dehydration and impaired digestion.

Estimating the volume of a spill

By observing the thickness of the film of oil and its appearance on the surface of the water, it is possible to estimate the quantity of oil spilled. If the surface area of the spill is also known, the total volume of the oil can be calculated.

Oil spill model systems are used by industry and government to assist in planning and emergency decision making. Of critical importance for the skill of the oil spill model prediction is the adequate description of the wind and current fields. There is a worldwide oil spill modelling (WOSM) program.

	Film Thickness		Quantity Spread
Appearance	in	mm	gal/sq ml	L/ha
Barely visible	0.0000015	0.0000380	25	0.370
Silvery sheen	0.0000030	0.0000760	50	0.730
First trace of color	0.0000060	0.0001500	100	1.500
Bright bands of color	0.0000120	0.0003000	200	2.900
Colors begin to dull	0.0000400	0.0010000	666	9.700
Colors are much darker	0.0000800	0.0020000	1332	19.500

Methods of cleaning

A sheen is usually dispersed (but not cleaned up) with detergents which makes oil settle to the bottom. Oils that are denser than water, such as Polychlorinated biphenyls (PCBs), can be more difficult to clean as they make the seabed toxic.

Methods for cleaning up include:

• Bioremediation: use of microorganisms or biological agents to break down or remove oil
• Controlled burning can effectively reduce the amount of oil in water, if done properly. But it can only be done in low wind, and can cause air pollution.
• Dispersants act as detergents, clustering around oil globules and allowing them to be carried away in the water. This improves the surface aesthetically, and mobilizes the oil. Smaller oil droplets, scattered by currents, may cause less harm and may degrade more easily. But the dispersed oil droplets infiltrate into deeper water and can lethally contaminate coral. Recent research indicates that some dispersants are toxic to corals.^[19]
• Watch and wait: in some cases, nautural attentuation of oil may be most appropriate, due to the invasive nature of facilitated methods of remediation, particularly in ecologically sensitive areas.
• Dredging: for oils dispersed with detergents and other oils denser than water.
• Skimming: Requires calm waters
• Solidifying

Equipment used includes:

• Booms: large floating barriers that round up oil and lift the oil off the water
• Skimmers: skim the oil
• Sorbents: large sponges that absorb oil
• Chemical and biological agents: helps to break down the oil
• Vacuums: remove oil from beaches and water surface
• Shovels and other road equipments: typically used to clean up oil on beaches

Prevention

• Secondary containment - methods to prevent releases of oil or hydrocarbons into environment.
• Oil Spill Prevention Containment and Countermeasures (SPCC) program by the United States Environmental Protection Agency.
• Double hulling - build double hulls into vessels, which reduces the risk and severity of a spill in case of a collision or grounding. Existing single-hull vessels can also be rebuilt to have a double hull.

Ocean Acidification

Ocean acidification is the name given to the ongoing decrease in the pH of the Earth's oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.179 to 8.104 (a change of -0.075).

Carbon cycle

In the natural carbon cycle, the atmospheric concentration of carbon dioxide (CO₂) represents a balance of fluxes between the oceans, terrestrial biosphere and the atmosphere. Human activities such as land-use changes, the combustion of fossil fuels, and the production of cement have led to a new flux of CO₂ into the atmosphere. Some of this has remained in the atmosphere (where it is responsible for the rise in atmospheric concentrations), some has been taken up by terrestrial plants, and some has been absorbed by the oceans.

When CO₂ dissolves, it reacts with water to form a balance of ionic and non-ionic chemical species : dissolved free carbon dioxide (CO_{2 (aq)}), carbonic acid (H₂CO₃), bicarbonate (HCO₃^-) and carbonate (CO₃^2-). The ratio of these species depends on factors such as seawater temperature and alkalinity (see the article on the ocean's solubility pump for more detail).

Acidification

Average surface ocean pH

Time	pH	pH change	Source
Pre-industrial (1700s)	8.179	0.000	analysed field
Recent past (1990s)	8.104	-0.075	field
2050 (2×CO2 = 560 ppm)	7.949	-0.230	model
2100 (IS92a)	7.824	-0.355	model

Dissolving CO₂ in seawater also increases the hydrogen ion (H⁺) concentration in the ocean, and thus decreases ocean pH. The use of the term "ocean acidification" to describe this process was introduced in Caldeira and Wickett (2003).

Since the industrial revolution began, it is estimated that surface ocean pH has dropped by slightly less than 0.1 units (on the logarithmic scale of pH), and it is estimated that it will drop by a further 0.3 - 0.5 units by 2100 as the ocean absorbs more anthropogenic CO₂.

Note that, although the ocean is acidifying, its pH is still greater than 7 (that of neutral water), so the ocean could also be described as becoming less alkaline.

Although the largest changes are expected in the future, a report from NOAA scientists found large quantities of water undersaturated in aragonite are already upwelling close to the Pacific continental shelf area of North America. Continental shelves play an important role in marine ecosystems since most marine organisms live or are spawned there, and though the study only dealt with the area from Vancouver to northern California, the authors suggest that other shelf areas may be experiencing similar effects. Similarly, one of the first detailed datasets examining temporal variations in pH at a temperate coastal location found that acidification was occurring at a rate much higher than that previously predicted, with consequences for near-shore benthic ecosystems.

Possible impacts

Although the natural absorption of CO₂ by the world's oceans helps mitigate the climatic effects of anthropogenic emissions of CO₂, it is believed that the resulting decrease in pH will have negative consequences, primarily for oceanic calcifying organisms. These use the calcite or aragonite polymorphs of calcium carbonate to construct cell coverings or skeletons. Calcifiers span the food chain from autotrophs to heterotrophs and include organisms such as coccolithophores, corals, foraminifera, echinoderms, crustaceans and molluscs.

Under normal conditions, calcite and aragonite are stable in surface waters since the carbonate ion is at supersaturating concentrations. However, as ocean pH falls, so does the concentration of this ion, and when carbonate becomes undersaturated, structures made of calcium carbonate are vulnerable to dissolution. Research has already found that corals, coccolithophore algae, coralline algae, foraminifera, shellfish and pteropods experience reduced calcification or enhanced dissolution when exposed to elevated CO₂. The Royal Society of London published a comprehensive overview of ocean acidification, and its potential consequences, in June 2005.

However, some studies have found different response to ocean acidification, with coccolithophore calcification and photosynthesis both increasing under elevated atmospheric pCO₂, an equal decline in primary production and calcification in response to elevated CO₂ or the direction of the response varying between species. Recent work examining a sediment core from the North Atlantic found that while the species composition of coccolithophorids has remained unchanged for the industrial period 1780 to 2004, the calcification of coccoliths has increased by up to 40% during the same time.

While the full ecological consequences of these changes in calcification are still uncertain, it appears likely that many calcifying species will be adversely affected. There is also a suggestion that a decline in the coccolithophores may have secondary effects on climate change, by decreasing the earth's albedo via their effects on oceanic cloud cover. Aside from calcification, organisms may suffer other adverse effects, either directly as reproductive or physiological effects (e.g. CO₂-induced acidification of body fluids, known as hypercapnia), or indirectly through negative impacts on food resources. However, as with calcification, as yet there is not a full understanding of these processes in marine organisms or ecosystems.

Leaving aside direct biological effects, it is expected that ocean acidification in the future will lead to a significant decrease in the burial of carbonate sediments for several centuries, and even the dissolution of existing carbonate sediments. This will cause an elevation of ocean alkalinity, leading to the enhancement of the ocean as a reservoir for CO₂ with moderate (and potentially beneficial) implications for climate change as more CO₂ leaves the atmosphere for the ocean.

Marine Debris

Marine debris, also known as marine litter, is human-created waste that has deliberately or accidentally become afloat in a lake, sea, ocean or waterway. Oceanic debris tends to accumulate at the centre of gyres and on coastlines, frequently washing aground, when it is known as beach litter.

Deliberate disposal of wastes at sea is called ocean dumping.

Some forms of marine debris, such as driftwood, occur naturally, and human activities have been discharging similar material into the oceans for thousands of years. Recently however, with the increasing use of plastic, human influence has become an issue as many types of plastics do not biodegrade. Waterborne plastic is both unsightly and dangerous, and poses a serious threat to fish, seabirds, marine reptiles, and marine mammals, as well as to boats and coastal habitations. Ocean dumping, accidental container spillages, and wind-blown landfill waste are all contributing to this problem.

Types of debris

A wide variety of anthropogenic artefacts can become marine debris; plastic bags, balloons, buoys, rope, medical waste, glass bottles and plastic bottles, cigarette lighters, beverage cans, styrofoam, lost fishing line and nets, and various wastes from cruise ships and oil rigs are among the items commonly found to have washed ashore. Six pack rings, in particular, are considered a poster child of the damage that garbage can do to the marine environment.

Studies have shown that eighty percent of marine debris is plastic – a component that has been rapidly accumulating since the end of World War II. Plastics accumulate because they don't biodegrade as many other substances do; although they will photodegrade on exposure to sunlight, they do so only under dry conditions, as water inhibits photolysis.

Ghost nets

Fishing nets left or lost in the ocean by fishermen – ghost nets – can entangle fish, dolphins, sea turtles, sharks, dugongs, crocodiles, seabirds, crabs, and other creatures. Acting as designed, these nets restrict movement, causing starvation, laceration and infection, and, in those that need to return to the surface to breathe, suffocation.

Nurdles and plastics bags

Nurdles, also known as mermaids' tears, are plastic pellets typically under five millimeters in diameter, and are a major component of marine debris. They are used as a raw material in plastics manufacturing, and are thought to enter the natural environment after accidental spillages. Mermaids' tears are also created by the physical weathering of larger plastic debris. Nurdles strongly resemble fish eggs.

Plastic shopping bags may clog digestive tracts when consumed. and may cause starvation through restricting the movement of food, or by filling the stomach and tricking the animal into thinking it is full. A 1994 study of the seabed using trawl nets in the North-Western Mediterranean around the coasts of Spain, France and Italy reported a particularly high mean concentration of debris; an average of 1,935 items per square kilometer. Plastic debris accounted for 77%, of which 93% was plastic bags.

Source of debris

It has been estimated that container ships lose over 10,000 containers at sea each year (usually during a storm). One famous spillage occurred in the Pacific Ocean in 1992, when thousands of rubber ducks and other toys went overboard during a storm. The toys have since been found all over the world; Curtis Ebbesmeyer and other scientists have used the incident to gain a better understanding of ocean currents. Similar incidents have happened before, with the same potential to track currents, such as when Hansa Carrier dropped 21 containers (with one notably containing buoyant Nike shoes). In 2007, MSC Napoli was beached in the English Channel, and dropped hundreds of containers, most of which washed up on the Jurassic Coast, a World Heritage Site.

Though it was originally assumed that most oceanic marine waste stemmed directly from ocean dumping, it is now thought that around four fifths of the oceanic debris is from rubbish blown seaward from landfills, and urban runoff washed down storm drains. In the 1987 Syringe Tide, medical waste washed ashore in New Jersey after having been blown from the Fresh Kills Landfill.

Legality of ocean and river dumping

Ocean dumping is controlled by international law:

• The London Convention (1972) – a United Nations agreement to control ocean dumping
• MARPOL 73/78 – an international convention designed to minimize pollution of the seas, including dumping, oil and exhaust pollution

European law

In 1972 and 1974, conventions were held in Oslo and Paris respectively, and resulted in the passing of the OSPAR Convention, an international treaty controlling marine pollution in the north-east Atlantic Ocean around Europe. A similar Barcelona Convention exists to protect the Mediterranean Sea. The Water Framework Directive of 2000 is a European Union directive committing EU member states to make their inland and coastal waters free from human influence. In the United Kingdom, the proposed Marine Bill is designed to "ensure clean healthy, safe, productive and biologically diverse oceans and seas, by putting in place better systems for delivering sustainable development of marine and coastal environment".

United States law

In 1972, the United States Congress passed the Ocean Dumping Act, giving the Environmental Protection Agency power to monitor and regulate the dumping of sewage sludge, industrial waste, radioactive waste and biohazardous materials into the nation's territorial waters. The Act was amended sixteen years later to include medical wastes. It is illegal to dispose of any plastic in all US waters. In 2008, the California State Legislature considered several bills aimed at reducing the sources of marine debris, following the recommendations of the California Ocean Protection Council.

Ownership of debris

Property law, admiralty law, and the law of the sea may be of relevance when lost, mislaid, and abandoned property is found at sea. Salvage law has as a basis that a salvor should be rewarded for risking his life and property to rescue the property of another from peril. On land the distinction between deliberate and accidental loss led to the concept of a "treasure trove". In the United Kingdom, shipwrecked goods should be reported to a Receiver of Wreck, and if identifiable, they should be returned to their rightful owner.

The Great Pacific Garbage Patch

Once waterborne, debris is far from immobile. Flotsam can be blown by the wind, or follow the flow of ocean currents, often ending up in the middle of oceanic gyres where currents are weakest. The Great Pacific Garbage Patch is one such example of this, comprising of a vast region of the North Pacific Ocean rich with anthropogenic wastes. Estimated to be double the size of Texas, the area contains more than 3 million tons of plastic. This means that there are approximately six pounds of plastic for every pound of plankton per cubic meter of seawater. The mass of plastic in our oceans may be as high as one hundred million tonnes.

Islands situated within gyres frequently have their coastlines ruined by the waste that inevitably washes ashore; prime examples are Midway and Hawaii. Clean-up teams around the world patrol beaches to clean up this environmental threat.

Environmental impact

Many animals that live on or in the sea consume flotsam by mistake, as it often looks similar to their natural prey. Plastic debris, when bulky or tangled, is difficult to pass, and may become permanently lodged in the digestive tracts of these animals, blocking the passage of food and causing death through starvation or infection. Tiny floating particles also resemble zooplankton, which can lead filter feeders to consume them and cause them to enter the ocean food chain. In samples taken from the North Pacific Gyre in 1999 by the Algalita Marine Research Foundation, the mass of plastic exceeded that of zooplankton by a factor of six.

Toxic additives used in the manufacture of plastic materials can leach out into their surroundings when exposed to water. Waterborne hydrophobic pollutants collect and magnify on the surface of plastic debris, thus making plastic far more deadly in the ocean than it would be on land. Hydrophobic contaminants are also known to bioaccumulate in fatty tissues, biomagnifying up the food chain and putting great pressure on apex predators. Some plastic additives are known to disrupt the endocrine system when consumed; others can suppress the immune system or decrease reproductive rates.

Not all anthropogenic artifacts in the oceans are harmful however. Iron and concrete do little damage to the environment as they are generally immobile, and can even be used as scaffolding for the creation of artificial reefs, increasing the biodiversity of a coastal region. Entire ships have been deliberately sunk in coastal waters for that purpose. Some organisms have adapted to live on mobile plastic debris, which has allowed the inhabitants to disperse all over the world and become invasive species in remote ecosystems.

Marine Pollution

Marine pollution occurs when harmful effects, or potentially harmful effects, can result from the entry into the ocean of chemicals, particles, industrial, agricultural and residential waste, or the spread of invasive organisms.

Most sources of marine pollution are land based. The pollution often comes from nonpoint sources such as agricultural runoff and wind blown debris.

Many potentially toxic chemicals adhere to tiny particles which are then taken up by plankton and benthos animals, most of which are either deposit or filter feeders. In this way, the toxins are concentrated upward within ocean food chains. Many particles combine chemically in a manner highly depletive of oxygen, causing estuaries to become anoxic.

When pesticides are incorporated into the marine ecosystem, they quickly become absorbed into marine food webs. Once in the food webs, these pesticides can cause mutations, as well as diseases, which can be harmful to humans as well as the entire food web.

Toxic metals can also be introduced into marine food webs. These can cause a change tissue matter, biochemistry, behaviour, reproduction, and suppress growth in marine life. Also, many animal feeds have a high fish meal or fish hydrolysate content. In this way, marine toxins can be transferred to land animals, and appear later in meat and dairy products.

History

Although marine pollution has a long history, significant international laws to counter it were enacted in the twentieth century. Marine pollution was a concern during several United Nations Conferences on the Law of the Sea beginning in the 1950s. Most scientists believed that the oceans were so vast that they had unlimited ability to dilute, and thus render harmless, pollution.. In the late 1950s and early 1960s, there were several controversies about dumping radioactive waste off the coasts of the United States by companies licensed by the Atomic Energy Commission, into the Irish Sea from the British reprocessing facility at Windscale, and into the Mediterranean Sea by the French Commissariat à l'Energie Atomique. After the Mediterranean Sea controversy, for example, Jacques Cousteau became a worldwide figure in the campaign to stop marine pollution. Marine pollution made further international headlines after the 1967 crash of the oil tanker Torrey Canyon, and after the 1969 Santa Barbara oil spill off the coast of California. Marine pollution was a major area of discussion during the 1972 United Nations Conference on the Human Environment, held in Stockholm. That year also saw the signing of the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, sometimes called the London Convention. The London Convention did not ban marine pollution, but it established black and gray lists for substances to be banned (black) or regulated by national authorities (gray). Cyanide and high-level radioactive waste, for example, were put on the black list. The London Convention applied only to waste dumped from ships, and thus did nothing to regulate waste discharged as liquids from pipelines.

Pathways of pollution

Bjorn Jenssen (2003) notes in his article, “Anthropogenic pollution may reduce biodiversity and productivity of marine ecosystems, resulting in reduction and depletion of human marine food resources” (p. A198). There are many different ways to categorize, and examine the inputs of pollution into our marine ecosystems. Patin (n.d.) notes that generally there are three main types of inputs of pollution into the ocean: direct discharge of waste into the oceans, runoff into the waters due to rain, and pollutants that are released from the atmosphere.

One common path of entry by contaminants to the sea are rivers. The Hudson in New York State and the Raritan in New Jersey, which empty at the northern and southern ends of Staten Island, are a source of mercury contamination of zooplankton (copepods) in the open ocean. The highest concentration in the filter-feeding copepods is not at the mouths of these rivers but 70 miles south, nearer Atlantic City, because water flows close to the coast. It takes a few days before toxins are taken up by the plankton.

Pollution is often classed as point source or nonpoint source pollution. Point source pollution occurs when there is a single, identifiable, and localized source of the pollution. An example is directly discharging sewage and industrial waste into the ocean. Pollution such as this occurs particularly in developing nations. Nonpoint source pollution occurs when the pollution comes from ill-defined and diffuse sources. These can be difficult to regulate. Agricultural runoff and wind blown debris are prime examples.

Pollution from ships

Ships can pollute waterways and oceans in many ways. Oil spills can have devastating effects. While being toxic to marine life, polycyclic aromatic hydrocarbons (PAHs), the components in crude oil, are very difficult to clean up, and last for years in the sediment and marine environment.

Discharge of cargo residues from bulk carriers can pollute ports, waterways and oceans. In many instances vessels intentionally discharge illegal wastes despite foreign and domestic regulation prohibiting such actions. Ships create noise pollution that disturbs natural wildlife, and water from ballast tanks can spread harmful algae and other invasive species.

Meinesz believes that one of the worst cases of a single invasive species causing harm to an ecosystem can be attributed to a seemingly harmless jellyfish. Mnemiopsis leidyi, a species of comb jellyfish that spread so it now inhabits estuaries in many parts of the world. It was first introduced in 1982, and thought to have been transported to the Black Sea in a ship’s ballast water. The population of the jellyfish shot up exponentially and, by 1988, it was wreaking havoc upon the local fishing industry. "The anchovy catch fell from 204,000 tons in 1984 to 200 tons in 1993; sprat from 24,600 tons in 1984 to 12,000 tons in 1993; horse mackerel from 4,000 tons in 1984 to zero in 1993". Now that the jellyfish have exhausted the zooplankton, including fish larvae, their numbers have fallen dramatically, yet they continue to maintain a stranglehold on the ecosystem.

Invasive species can take over once occupied areas, facilitate the spread of new diseases, introduce new genetic material, alter underwater seascapes and jeopardize the ability of native species to obtain food. Invasive species are responsible for about $138 billion annually in lost revenue and management costs in the US alone.

Plastic debris

Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Eighty percent of marine debris is plastic - a component that has been rapidly accumulating since the end of World War II. The mass of plastic in the oceans may be as high as one hundred million tonnes.

Discarded plastic bags, six pack rings and other forms of plastic waste which finish up in the ocean present dangers to wildlife and fisheries. Aquatic life can be threatened through entanglement, suffocation, and ingestion. Fishing nets, usually made of plastic, can be left or lost in the ocean by fishermen. Known as ghost nets, these entangle fish, dolphins, sea turtles, sharks, dugongs, crocodiles, seabirds, crabs, and other creatures, restricting movement, causing starvation, laceration and infection, and, in those that need to return to the surface to breathe, suffocation.

Many animals that live on or in the sea consume flotsam by mistake, as it often looks similar to their natural prey. Plastic debris, when bulky or tangled, is difficult to pass, and may become permanently lodged in the digestive tracts of these animals, blocking the passage of food and causing death through starvation or infection.

Plastics accumulate because they don't biodegrade in the way many other substances do. They will photodegrade on exposure to the sun, but they do so properly only under dry conditions, and water inhibits this process. In marine environments, photodegraded plastic disintegrates into ever smaller pieces while remaining polymers, even down to the molecular level. When floating plastic particles photodegrade down to zooplankton sizes, jellyfish attempt to consume them, and in this way the plastic enters the ocean food chain. Many of these long-lasting pieces end up in the stomachs of marine birds and animals, including sea turtles, and black-footed albatross.

Plastic debris tends to accumulate at the centre of ocean gyres. In particular, the Great Pacific Garbage Patch has a very high level of plastic particulate suspended in the upper water column. In samples taken in 1999, the mass of plastic exceeded that of zooplankton (the dominant animal life in the area) by a factor of six.

Toxic additives used in the manufacture of plastic materials can leech out into their surroundings when exposed to water. Waterborne hydrophobic pollutants collect and magnify on the surface of plastic debris, thus making plastic far more deadly in the ocean than it would be on land. Hydrophobic contaminants are also known to bioaccumulate in fatty tissues, biomagnifying up the food chain and putting pressure on apex predators. Some plastic additives are known to disrupt the endocrine system when consumed, others can suppress the immune system or decrease reproductive rates. Floating debris can also absorb persistent organic pollutants from seawater, including PCBs, DDT and PAHs. Aside from toxic effects, when ingested some of these are mistaken by the animal brain for estradiol, causing hormone disruption in the affected wildlife.

Toxins

Apart from plastics, there are particular problems with other toxins that do not disintegrate rapidly in the marine environment. Examples of persistent toxins are PCBs, DDT, pesticides, furans, dioxins and phenols. Heavy metals are metallic chemical elements that have a relatively high density and are toxic or poisonous at low concentrations. Examples are mercury, lead, nickel, arsenic and cadmium.

Such toxins can accumulate in the tissues of many species of aquatic life in a process called bioaccumulation. They are also known to accumulate in benthic environments, such as estuaries and bay muds: a geological record of human activities of the last century.

Eutrophication

Eutrophication is an increase in chemical nutrients, typically compounds containing nitrogen or phosphorus, in an ecosystem. It can result in an increase in the ecosystem's primary productivity (excessive plant growth and decay), and further effects including lack of oxygen and severe reductions in water quality, fish, and other animal populations.

The biggest culprit are rivers that empty into the ocean, and with it the many chemicals used as fertilizers in agriculture as well as waste from livestock and humans. An excess of oxygen depleting chemicals in the water can lead to hypoxia and the creation of a dead zone.

Estuaries tend to be naturally eutrophic because land-derived nutrients are concentrated where runoff enters the marine environment in a confined channel. The World Resources Institute has identified 375 hypoxic coastal zones around the world, concentrated in coastal areas in Western Europe, the Eastern and Southern coasts of the US, and East Asia, particularly in Japan. In the ocean, there are frequent red tide algae blooms that kill fish and marine mammals and cause respiratory problems in humans and some domestic animals when the blooms reach close to shore.

In addition to land runoff, atmospheric anthropogenic fixed nitrogen can enter the open ocean. A study in 2008 found that this could account for around one third of the ocean’s external (non-recycled) nitrogen supply and up to three per cent of the annual new marine biological production. It has been been suggested that accumulating reactive nitrogen in the environment may have consequences as serious as putting carbon dioxide in the atmosphere.

Acidification

The oceans are normally a natural carbon sink, absorbing carbon dioxide from the atmosphere. Because the levels of atmospheric carbon dioxide are increasing, the oceans are becoming more acidic. The potential consequences of ocean acidification are not fully understood, but there are concerns that structures made of calcium carbonate may become vulnerable to dissolution, affecting corals and the ability of shellfish to form shells.

A report from NOAA scientists published in the journal Science in May 2008 found that large amounts of relatively acidified water are upwelling to within four miles of the Pacific continental shelf area of North America. This area is a critical zone where most local marine life lives or is born. While the paper dealt only with areas from Vancouver to northern California, other continental shelf areas may be experiencing similar effects.

Specific examples

• Chinese and Russian industrial pollution such as phenols and heavy metals in the Amur River have devastated fish stocks and damaged its estuary soil

• Wabamun Lake in Alberta, Canada, once the best whitefish lake in the area, now has unacceptable levels of heavy metals in its sediment and fish.

• Acute and chronic pollution events have been shown to impact southern California kelp forests, though the intensity of the impact seems to depend on both the nature of the contaminants and duration of exposure.

• Ballast water taken up at sea and released in port is a major source of unwanted exotic marine life. The invasive freshwater zebra mussels, native to the Black, Caspian and Azov seas, were probably transported to the Great Lakes via ballast water from a transoceanic vessel.

• Due to their high position in the food chain and the subsequent accumulation of heavy metals from their diet, mercury levels can be high in larger species such as bluefin and albacore. As a result, in March 2004 the United States FDA issued guidelines recommending that pregnant women, nursing mothers and children limit their intake