Vehicle exhausts and industrial chimneys are large sources of nitrogen compounds that are transported in the atmosphere and deposited in coastal waters. On a global scale, agricultural runoff is the most important source of eutrophication, but atmospheric deposition is the fastest-growing source. It is the largest source of nitrogen off the coast of the northeastern United States , in the western Baltic Sea , and in the western Mediterranean Sea.
International agencies consider that, worldwide, eutrophication is the most serious pollution problem in coastal waters. For example, in the Gulf of Mexico , off the mouth of the Mississippi River , water near the bottom has severely reduced oxygen content over a very large area, sixteen thousand square kilometers 6, square miles by Mobile animals such as fish and shrimp leave the hypoxic area, but sedentary animals such as clams and worms are killed in large numbers.
A classic example of eutrophication and its treatment occurred in the estuary of the River Thames, near London, England. In the s the water was severely hypoxic for thirty-five kilometers twenty-two miles below London Bridge. After several sewage treatment plants were built, the water returned to a well-oxygenated state and migratory fish such as salmon once again ascend the river.
In the case of the Mississippi River, treatment of the eutrophication is more difficult because runoff from agricultural land is the major cause of the problem, and more than half of the agricultural land in the United States drains into the Mississippi basin. Cleaning up the pollution would involve changes in farming methods on a national scale. Eutrophication has important indirect effects. The plants known as sea grasses, which grow in the shallow water of estuaries , provide food and shelter for a wide range of animals, including geese, turtles, manatees, and fish.
In eutrophicated water, the dense microscopic plant life significantly reduces the penetration of light and smothers the sea grasses. In Chesapeake Bay , Maryland , eutrophication caused an area of sea grasses to decrease by twothirds between and , and there was a corresponding decrease in landings of fish and crabs. Similar effects have been observed in Australia. Red tides, or harmful algal blooms, are associated with eutrophication. Single species of phytoplankton multiply at the expense of all other species and become so abundant that the water is discolored. Many bloom species produce toxic substances.
During the s in estuaries located in the southeastern United States , there were numerous cases of blooms of Pfiesteria piscida, a dinoflagellate that produced a toxin which killed thousands of fish. The source of the nutrients support Pfiesteria is believed to be agricultural runoff or sewage discharge. Other types of blooms are ingested by shellfish, which become toxic for humans who consume them, causing partial paralysis, memory loss, or even death. Toxic blooms have been reported much more frequently in the s than in the past, and the spread of eutrophication is believed to be a contributing factor.
On coral reefs , eutrophication causes seaweed to grow and smother the corals. Several kinds of environmental problems interact with eutrophication to cause the deterioration of coral reefs. Overharvesting of the fish and invertebrates that eat seaweed accelerates the smothering. Careless development along coastlines and in river basins leads to soil erosion and the transport of heavy loads of silt and clay, which settle on the corals and smother them. Oil spills also take their toll. When corals are exposed to abnormally high water temperature, they respond by discharging the microscopic algae living within their tissues.
Sometimes they recover, but often they die. These episodes, called coral bleaching, became much more frequent during the s and are believed to be caused by global warming. The result of pollution and global warming is that at least half of the area of coral reefs in southeast Asia is in poor condition, and in parts of the Caribbean Sea only 5 percent of the reef area consists of living coral. Industrial effluents often contain metallic compounds.
For example, Halifax, a small city in eastern Canada , discharged into its harbor during the s about thirty-three tons of zinc and thirty-one tons of lead per year, with lesser amounts of copper and other metals. These metals are held in the sediment in a relatively inert form, but if stirred up into the water column, they become oxygenated and toxic.
Tin is another common pollutant in harbors. It occurs as tributyltin TBT , which is used as a component of antifouling paints on the undersides of ships. When taken up by shellfish, it accumulates in their tissues and has proved toxic to the shellfish and to organisms that consume them. The United States began to phase out TBT in , and it will be banned internationally beginning in Industry also produces organic compounds such as polychlorinated biphenyls PCBs and various pesticides.
These accumulate in the fatty tissue of plants and animals low in the food chain , and as they pass through the food web to larger and long-lived animals, there is an increase in concentration of the substances in their fat, a process known as bioaccumulation.
The St. Lawrence River, which drains the Great Lakes , has accumulated large amounts of organochlorines , which have amassed in the tissues of Beluga whales. During the s, the level of this pollution was much reduced, and the whales have been protected from hunting, but their population fails to increase. Many animals have tumors and disease. There is mounting evidence that chronic exposure to contaminants causes suppression of the immune responses of marine mammals.
Similar problems have occurred with seals in the Baltic Sea. The most serious types of oil pollution occur when an oil tanker goes ashore or hits a reef and spills its contents. As the oil drifts ashore, great damage is done to beaches, rocky shores, salt marshes, or mangrove forests. Cleanup is often attempted using mechanical means, or the application of dispersants, with mixed results. Usually, a proportion of native organisms are killed, but given time, the lighter fractions of oil evaporate, while the heavier fractions are decomposed by photochemical processes and microorganisms.
International law now requires that vessel owners be responsible for any loss of oil, damage to existing ecosystems, and the costs of recommended cleanup. Chronic low levels of oil pollution, resulting from accidental spills when loading or unloading, or from washing out oil tanks, are widespread and of significant concern. For example, it has been determined that corals around an oil terminal in the Red Sea have experienced lower growth rates and poor reproduction as a result of chronic low-level oil pollution.
Oil pollution of the open ocean is also a major concern. When Thor Heyerdahl crossed the South Pacific on the raft Kon-Tiki in he reported pristine waters, but his Ra expedition across the Atlantic twenty-two years later encountered oil slicks on forty-three of fifty-seven days at sea. The International Convention for Prevention of Pollution from Ships was devised in and modified by the Protocol of Oceangoing vessels are subject to strict regulations concerning the discharge of oil, bilge water, and ballast water, and are forbidden to dump garbage and other solid waste.
Accidental spills must be reported. Marine beaches serve as natural traps for marine debris. Globally, the most common materials are plastics, followed by glass and metal. The chief dangers to marine life result from the ingestion of these fragments, which may block the gut, and from entangling, which may cause suffocation or prevent locomotion and feeding. In a survey of U. A high proportion of this material reached the sea by way of sewers.
Even street litter can be washed into surface drains and then to the sea. The dumping of sewage and waste by ships is another source. Public revulsion at the state of U. On sites more remote from cities, pieces of rope and netting are the most common types of marine debris. There is much that individuals can do to prevent marine pollution: avoid putting toxic substances into drains, avoid dropping litter, minimize the use of pesticides and fertilizers, reduce automobile emissions, and pressure your local government for sewage treatment in the community if it does not yet exist.
Larger-scale problems require legislation and enforcement, ranging from the local laws of coastal states in the United States, through national laws such as the Clean Water Act and Clean Air Act , to international conventions such as the International Convention for the Prevention of Pollution from Ships. Such laws are effective only if they have the support of the people.
Coral grows a new layer each year, much as a tree adds a new ring each year. Scientists analyzing layers of Bermudan coral have discovered an environmental record dating back to the mids. Marine pollution can be measured across the Industrial Revolution. Marine levels of lead have dropped dramatically since the phaseout of leaded gasoline but levels of lead in the Atlantic are still double their preindustrial concentrations.
When Thor Heyerdahl , a Norwegian biologist — , sailed the balsa wood raft named Kon-Tiki, from Peru to Polynesia in , he saw no pollution in the Pacific Ocean. Just over twenty years later, in , when sailing a papyrus reed boat from Morocco to Barbados, Heyerdahl saw extensive marine pollution including oily wastes, plastic bottles and other trash floating in the water. He radioed the United Nations to report that floating lumps of solidified, asphalt-like oil polluted over one thousand miles of the Atlantic Ocean.
After seeing the extent of the ocean's pollution first hand, Heyerdahl became actively involved in fighting marine pollution. In , with the Norwegian Shipowners Organization, he initiated the Thor Heyerdahl International Maritime Environmental Award to be given for improvement of the global environment. Thousands of volunteers in every U. The Ocean Conservancy, which organizes the annual cleanup, collects data on the debris to determine sources of pollution.
The most common item washed up on the shoreline? Cigarette butts and filters — a total of 1,, were picked up in Volunteers also found entangled animals, most snared in nylon fishing line. Water pollution occurs when undesirable foreign substances are introduced into natural water. The substances may be chemical or biological in nature.
Common pollutants include human or animal waste; disease-producing organisms; radioactive materials; toxic metals such as lead or mercury; agricultural chemicals such as pesticides, herbicides, or fertilizers; acid rain ; and high-temperature water discharged from power plants, often called "thermal pollution. High temperatures may cause algae to grow rapidly, rendering water unfit for consumption. Point sources of pollution, such as an oil leak from a pipeline or chemical waste from a factory, can often be controlled.
Nonpoint sources, such as runoff sediment and nitrate-rich water from feedlots represent larger amounts of pollution and are difficult to identify and remedy. Pollution from nonpoint sources may pass into streams or aquifers, covering a wide area. Although water has been identified on several planets, none has as much water as Earth , of which 70 percent is covered with water.
Approximately An additional 2. Less than 0. In a few places, water is pure enough to drink directly from wells or springs, but increasingly water must be treated to remove dangerous contaminants, and substances such as chlorine, chloramines, or ozone must be added to kill harmful bacteria. Pollutants in water are commonly measured and reported as parts per million ppm or parts per billion ppb. A solution that contains 2 grams 0. A 1 ppb solution of calcium contains 1 gram 0. A concentration of 1 ppm is the same as 1 milligram 3. While it is impractical to remove all impurities from water, the Safe Drinking Water Act, passed by the U.
Congress in , gives the Environmental Protection Agency EPA the authority to set limits for harmful contaminants in water. This level is defined as the amount of impurity that could be present in two liters of water drunk by a person weighing 70 kilograms pounds , each day for seventy years, without ill effects.
A single exposure to concentrations of pollutants below the MCL is considered to be harmless. The MCLG of lead is 0; continuous exposure to lead in any concentration is considered hazardous. The MCL of lead is 0. Specialized analytical equipment allows technicians to monitor pollutants. In the field, pH meters are used to measure acidity and turbidometers measure the presence of suspended solids.
Samples taken to laboratories are analyzed by gas chromatography to determine the presence of organic. Such instruments are capable of detecting as little as one part per trillion of pollutants in water. For much of history, humans used waterways and bodies of water as waste dumps. When the human population was low, fewer people were exposed to the effects of pollution, and the sources were fewer and produced less pollution.
During the Industrial Revolution of the nineteenth century, water pollution was recognized as a danger to public health. Even early settlers were concerned with water quality. Two hundred years before laws were written to protect consumers from lead poisoning , Benjamin Franklin wrote of a family that suffered gastrointestinal pains after drinking water collected from their lead roof. During the trek west, members of wagon trains avoided drinking from stagnant pools, some of which contained large amounts of alkali.
As populations and production grew, industrial and household refuse accumulated, and it became clear that many discarded materials did not simply disappear, but were spread through the water table , absorbed by lower forms of life and passed up the food chain , causing deaths, birth defects , and mental problems.
Now, many beaches are closed occasionally or permanently due to pollution, and at a time when populations of fish have decreased, many areas are unsafe for fishing. Water pollution represents an especially dangerous problem in developing nations, which have high populations and manufacturing facilities that do not meet safety standards. The most dangerous forms of water pollutants include sewage, which frequently contains dangerous pathogenic organisms; oil and hydrocarbons; heavy metals; radioactive substances; pesticides and herbicides; and corrosive substances such as acids and bases.
In developed countries, few direct sources of water pollution should exist, but homeowners still discharge motor oil, antifreeze, pet waste, and paint into storm sewers, and small manufacturers sometimes ignore proper disposal procedures. In developing countries, businesses and households often discharge wastes directly into streams or ponds that are also used for water supplies. Many sources contaminate water supplies indirectly. Indirect sources of pollution include runoff of waste from feedlots or runoff of agricultural chemicals from farmlands; leaking oil from pipelines, wells, or platforms; and large amounts of sediment from streets and parking lots.
Most industrial operations are required to treat wastewater before discharging it into rivers. Wastes from feedlots are collected in lagoons, settled, collected, and used for fertilizer.
Heavy metals and organic compounds from industry are often reclaimed from wastewater and recycled, decreasing manufacturing costs. Sewage from homes undergoes at least two stages of treatment. Primary treatment consists of sedimentation and dyeing of solids, which may be used as fertilizer. Secondary treatment consists of aeration of the remaining liquid, through a process of stirring, trickling over filters, and spraying; aerobic bacteria oxidize much of the remaining organic matter.
Tertiary treatment, using antibacterial agents such as chlorine or ozone, may be used to produce effluent water that is safe for further use. MacKenzie, Susan Hill Washington, DC: Island Press. Stanitski, Conrad L. Chemistry in Context: Applying Chemistry to Society, 4th edition. Boston: McGraw-Hill. Industrial Pollution In the United States industry is the greatest source of pollution, accounting for more than half the volume of all water pollution and for the most deadly pollutants.
Some , manufacturing facilities use huge quantities of freshwater to carry away wastes of many kinds. The waste-bearing water, or effluent, is discharged into streams, lakes, or oceans, which in turn disperse the polluting substances. The pollutants include grit, asbestos , phosphates and nitrates , mercury , lead , caustic soda and other sodium compounds, sulfur and sulfuric acid , oils, and petrochemicals.
In addition, numerous manufacturing plants pour off undiluted corrosives, poisons, and other noxious byproducts. The construction industry discharges slurries of gypsum, cement, abrasives, metals, and poisonous solvents. Another pervasive group of contaminants entering food chains is the polychlorinated biphenyl PCB compounds, components of lubricants, plastic wrappers, and adhesives. In yet another instance of pollution, hot water discharged by factories and power plants causes so-called thermal pollution by increasing water temperatures. Such increases change the level of oxygen dissolved in a body of water, thereby disrupting the water's ecological balance, killing off some plant and animal species while encouraging the overgrowth of others.
Other Sources of Water Pollution Towns and municipalities are also major sources of water pollution. In many public water systems, pollution exceeds safe levels. One reason for this is that much groundwater has been contaminated by wastes pumped underground for disposal or by seepage from surface water. When contamination reaches underground water tables, it is difficult to correct and spreads over wide areas.
In addition, many U. Along with domestic wastes, sewage carries industrial contaminants and a growing tonnage of paper and plastic refuse see solid waste. Although thorough sewage treatment would destroy most disease-causing bacteria, the problem of the spread of viruses and viral illness remains.
Additionally, most sewage treatment does not remove phosphorus compounds, contributed principally by detergents, which cause eutrophication of lakes and ponds. Excreted drugs and household chemicals also are not removed by present municipal treatment facilites, and can be recycled into the drinking water supply. Rain drainage is another major polluting agent because it carries such substances as highway debris including oil and chemicals from automobile exhausts , sediments from highway and building construction, and acids and radioactive wastes from mining operations into freshwater systems as well as into the ocean.
Also transported by rain runoff and by irrigation return-flow are animal wastes from farms and feedlots, a widespread source of pollutants impairing rivers and streams, groundwater, and even some coastal waters. Antibiotics, hormones, and other chemicals used to raise livestock are components of such animal wastes. Pesticide and fertilizer residues from farms also contribute to water pollution via rain drainage.
Ocean Pollution Large and small craft significantly pollute both inland and coastal waters by dumping their untreated sewage. Oil spilled accidentally or flushed from tankers and offshore rigs , metric tons annually sullies beaches and smothers bird, fish, and plant life. In in one of the world's worst single instances of water pollution, the Amoco Cadiz broke in two on the coast of Brittany, France, and spilled 1.
Oil well blowouts during offshore drilling, such as the Ixtoc 1 blowout in Gulf of Mexico off Mexico and the Deepwater Horizon blowout in the Gulf of Mexico off Louisiana, have also caused severe oil pollution. In addition to its direct damage to wildlife, oil takes up fat-soluble poisons like DDT, allowing them to be concentrated in organisms that ingest the oil-contaminated water; thus such poisons enter the food chains leading to sea mammals and people see ecology. In addition, tarry oil residues are encountered throughout the Atlantic, as are styrofoam and other plastic rubbish.
Plastic bits litter sections of the Pacific and Atlantic, accumulating in greater concentrations to form "garbage patches" where the currents are slack. Garbage, solid industrial wastes, and sludge formed in sewage treatment, all commonly dumped into oceans, are other marine pollutants found worldwide, especially along coastal areas.
Dangers of Water Pollution Virtually all water pollutants are hazardous to humans as well as lesser species; sodium is implicated in cardiovascular disease, nitrates in blood disorders. Mercury and lead can cause nervous disorders. Some contaminants are carcinogens. DDT is toxic to humans and can alter chromosomes. PCBs cause liver and nerve damage, skin eruptions, vomiting, fever, diarrhea, and fetal abnormalities.
Along many shores, shellfish can no longer be taken because of contamination by DDT, sewage, or industrial wastes. Dysentery , salmonellosis , cryptosporidium , and hepatitis are among the maladies transmitted by sewage in drinking and bathing water. In the United States, beaches along both coasts, riverbanks, and lake shores have been ruined for bathers by industrial wastes, municipal sewage, and medical waste. Water pollution is an even greater problem in the Third World , where millions of people obtain water for drinking and sanitation from unprotected streams and ponds that are contaminated with human waste.
This type of contamination has been estimated to cause more than 3 million deaths annually from diarrhea in Third World countries, most of them children. Legislation and Control The United States has enacted extensive federal legislation to fight water pollution. Limitation of ocean dumping was proposed at the nation London Conference of , and in the same year 12 European nations meeting in Oslo adopted rules to regulate dumping in the North Atlantic.
An international ban on ocean dumping in set further restrictions. Water pollution exists when water is contaminated by impurities or its quality is otherwise adversely affected, for example, by solid matter or thermal discharges. Water pollution problems have a long history that can be traced to antiquity, and the attempts of communities to control such problems have an equally long track record. The nature of water pollution problems has changed over time, and their geographic scale has steadily increased, as has the scale of institutional solutions that have been adopted to control them.
This entry explores the key changes in the nature and scale of water pollution and in the institutional solutions that have been adopted as a response to it. These problems were initially local, when wells and ground water were used for water supplies, and communities responded to them with local public health and sanitation regulations.
The construction of networked water supplies and sewer systems after the mids increased the scale of water pollution.
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Local regulations proved powerless when sources of pollution were increasingly outside the local jurisdiction. This situation gave rise to the first state and national water pollution policies, which successfully safeguarded public health but which largely failed to improve in-stream water quality. The nature of water pollution changed in industrialized countries around the time of World War II — because the war effort and postwar reconstruction resulted in the rapid growth of industrial production and increased discharge of industrial effluents.
New innovations such as organic pesticides and synthetic detergents also proved potent water pollutants. Furthermore, there was controversy over asbestos-containing discharges from Reserve Mining into Lake Superior in Silver Bay, Minnesota , in the s; the leak of toxic chemicals from the Sandoz factory in Basel , Switzerland , in ; and the cyanide spill from a gold mine in Baia Mare, Romania , which polluted the Tisza and Danube rivers in More recently, in November , an explosion in a chemical plant in Jilin , China , polluted the Songhua River with benzene and nitrobenzene.
Water pollution continues to be a public health problem in the developing world. Worldwide, one child out of six under five years of age dies of a diarrheal disease such as cholera, typhoid fever , dysentery, and gastroenteritis, which are caused by the contamination of water by human wastes. Moreover, weak enforcement or the nonexistence of environmental and safety regulations in developing countries means that agriculture, horticulture, and mining are major sources of toxic water pollutants such as pesticides and mercury.
Such pollutants have caused grave public health consequences across the developing world, but particularly in severely polluted areas such as the Aral Sea region in Central Asia. In some places, such as in Bangladesh , naturally occurring arsenic pollutes certain layers of ground water on which many communities depend for their water supply. Most developed countries have adopted water pollution policies that have reduced conventional water pollutants from point sources. Conventional pollutants include biochemical oxygen demand BOD , total suspended solids TSS , fecal coliform, oil and grease, and pH acidity and alkalinity.
Point sources include municipal sewage treatment plants, industrial establishments, and other facilities, which only contributed about half of all conventional pollutants in the United States when the Clean Water Act of , with its focus on point sources, was adopted. Water pollution originating from nonpoint sources, such as agriculture, streets and roads, and storm sewers, was not originally controlled with the same level of effectiveness.
National policies have also been less successful in reducing the amount of nonconventional pollutants, such as those of toxic chemicals. More recently, market-based instruments such as fertilizer, manure, and pesticide taxes have been used in many countries for controlling water pollution from nonpoint sources.
Other market based instruments, particularly tradable effluent permits and sewerage charges, have increasingly been used also for controlling conventional water pollutants. The incentives and capacity of states to control pollution from sources that lie outside their jurisdictions is limited, however. International environmental agreements have been negotiated to address this problem, including early agreements on the transportation of dangerous substances on the River Rhine in western Europe, which came into force between and , and the Boundary Waters Treaty between the United States and Canada , which took effect in International agreements since have addressed, for example, the pollution of the marine environment by oil and dumping; the pollution of transboundary bodies of water such as the Baltic Sea , the North Sea , and the Mediterranean; the elimination of persistent organic compounds; and the international transport of hazardous materials and liability for damages caused by their transport.
Some of these conventions, such as the Baltic Sea Convention, have been successful, while others have made little difference to the quality of the marine environment to date. Andrews, Richard N. Jamison, Dean T. Disease Control Priorities in Developing Countries. New York : Oxford University Press. Kirchner, Andree, ed. Paavola, Jouni. Law: Water and Air Pollution. McNeill, and Carolyn Merchant, — London and New York: Routledge. Tarr, Joel A. W ater pollution may derive from several sources, including chemical pollutants from industry, runoff of chemicals used in agriculture, or debris from geological process, but the greatest source of pollution is organic waste.
Although chemical pollutants may become diluted, they can also radically alter the ecosystem to allow the overproduction of certain forms of algae and bacteria that pollute the water with respect to its use by humans. Once in the water, the growth of microorganisms can be exacerbated by environmental factors such as the water temperature and the chemical composition of the water. For example, runoff of fertilizers from suburban properties can infuse watercourses with nitrogen, potassium, and phosphorus.
All these are desirable nutrients for bacterial growth. With specific respect to microorganisms, water pollution refers to the presence in water of microbes that originated from the intestinal tract of humans and other warm-blooded animals. Water pollution can also refer to the presence of compounds that promote the growth of the microbes. The remediation of polluted water — the removal of the potentially harmful microorganisms or the reduction of their numbers to acceptable levels — represents the purification of water. Microorganisms that reside in the intestinal tract find their way into fresh and marine water when feces contaminate the water.
Examples of bacteria that can pollute water in this way are Escherichia coli , Salmonella, Shigella , and Vibrio cholerae.
Warm-blooded animals other than humans can also contribute protozoan parasites to the water via their feces. The two prominent examples of health relevance to humans are Cryptosporidium parvum and Giardia lamblia. The latter two species are becoming more common. They are also resistant to chlorine, the most popular purification chemical. Normally, the intestinal bacteria do not survive long in the inhospitable world of the water. However, if they are ingested while still living, they can cause maladies, ranging from inconvenient intestinal upset to life-threatening infections.
An example of the latter is Escherichia coli OH7. Pollution of the water with this strain can cause severe intestinal damage, life-long damage to organs such as the kidney, and — especially in the young, elderly, and those whose immune systems are compromised — death. There are several common ways in which microorganisms can pollute water. Runoff from agricultural establishments,. Seasonal runoff can occur, especially in the springtime when rainfall is more pronounced. Water purification seeks to convert the polluted water into water that is acceptable for drinking, for recreation, or for some other purpose.
Techniques such as filtration and exposure to agents or chemicals that will kill the microorganisms in the water are common means of purification. The use of chlorination remains the most widely used purification option. Other approaches are the use of ultraviolet radiation , filters of extremely small pore size such that even viruses are excluded , and the use of a chemical known as ozone.
Depending on the situation and the intended use of the finished water, combinations of these techniques can be used. Purification of drinking water aims to remove as many bacteria as possible, and eliminate those bacteria of intestinal origin. Recreational waters need not be pristine.
But bacterial numbers need to be below whatever standard has been deemed permissible for the particular locale. Another microbiological aspect of water pollution that has become recognized only within the past several years has been the presence in water of agents used to treat bacteria in other environments. For example, a number of disinfectant compounds are routinely employed in the cleaning of household surfaces.
In the hospital, the use of antibiotics to kill bacteria is an everyday occurrence. Such materials have been detected in water both before and after municipal wastewater treatment. The health effect of these compounds is not known at the present time. However, looking at similar situations, the low concentration of such compounds might propogate the development of resistant bacterial populations. Natural wetlands also contribute to the purification of water. Wetlands can serve as a depositional sump and provide biological filtering. Normal percolation through soil layers also provides a significant source of water purification.
With respect to microorganisms , water pollution refers to the presence in water of microbes that originated from the intestinal tract of humans and other warm-blooded animals. The remediation of polluted water — the removal of the potentially harmful microorganisms — or the reduction of their numbers to levels considered to be acceptable for whatever purpose the water is used, represents the purification of water.
Examples of bacteria that can pollute water in this way are Escherichia coli , Salmonella , Shigella , and Vibrio cholerae. The latter two species are becoming more prominent. But, if they are ingested while still living, they can cause maladies, ranging from inconvenient intestinal upset to life-threatening infections.
A prominent example of the latter is Escherichia coli OH7. Pollution of the water with this strain can cause severe intestinal damage, life long damage to organs such as the kidney and — especially in the young, elderly and those whose immune systems are compromised — death. Runoff from agricultural establishments, particularly where livestock is raised, is one route of contamination. The feeding of birds e. For example, a large numbers of ducks that congregate can contribute large quantities of fecal material to localized ponds and lakes. Once in the water, the growth of microorganisms can be exacerbated by environmental factors such as the water temperature, and by the chemical composition of the water.
Others approaches are the use of ultraviolet radiation , filters of extremely small pore size such that even viruses are excluded , and the use of a chemical known as ozone. Purification of drinking water aims to remove as many bacteria as possible, and to completely eliminate those bacteria of intestinal origin. Ricci, ed. DOI Nanda, ed. Peacock; general eds. Palo Alto, Cal.
In the last third of the twentieth century, a renewed interest in the aesthetics of nature emerged. This has been observed in cases where a new metal smelter was constructed in a forested landscape and proceeded to emit large amounts of pollutants, such as sulphur dioxide and metals. In general, organisms are tolerant of an exposure to relatively small concentrations of potentially toxic substances, and some chemicals may even accumulate in their tissues without causing discernible harm. On the contrary, the discipline was dominated by an interest in art. Large inscription on front endpaper in red marker. In he received a vocation to the North Rhine-Westphalian academy of science and art.
San Antonio: Trinity University Press, : Nelson Athens: University of Georgia Press, : Vrin, : Michael Scott, Dale D. Goble, Frank W. Groom, Gary K. Meffe, C. Tonella, ed. Pahl-Wostl, S. Schmidt, A. Rizzoli, A. Jakeman, eds. Valdes, ed. Mooney, Walter V. Reid, et al. Dallmeyer, ed. Verso uno sviluppo umano e sostenibile Milano: Franco Angeli, : Knight, ed.
Cole and Stephen F. McCool, Wayne A. Paul: Pheasants Forever, : Mumford in Jackie Hitz and Karen Gaul, eds. Freyfogle in For the Health of the Land: Meffe and C. Ronald Carroll, eds. Nielsen and Dennis A. Powers, eds. Marietta and Lester Embree, eds. Overholt in Robert Solomon and Kathleen Higgins, eds. Wallace Covington and Leonard F. Debano, eds. Department of Agriculture, : Overholt, in Robert Solomon and Kathleen Higgins, eds. Stuhr and Robin M. Cochran, eds. Decker, M. Krasny, G. Goff, and C. Smith, eds. Olson, ed. Allen and D. Van Dusen, eds. Decker and Gary Goff, eds.
This work, one of Springer's renowned and authoritative Major Reference Works, contributes to these goals in several ways. First, it comprises a number of entries, consisting of both in-depth essays and definitions. Secondly, the content has been improved even more by adding additional tables and high-quality figures. Thirdly, the extensive linking between definitions and essays facilitates information within a minimum of time.
International contributors, who are well-known specialists in their fields, give a comprehensive review of all parasites and therapeutic strategies in veterinarian and human parasitology. This 4th edition presents all important parasites of humans and animals in detail and the less important ones in short.
Existing entries are updated and presented in the light of the latest knowledge. In he obtained a doctorate under Prof. In he worked as an assistant at Universites in France and the US.