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Water pollution

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Water pollution

Water pollution is a term that describes any adverse effect upon water bodies (lakes, rivers, the sea, groundwater etc.) caused by man and his activities. Although natural phenomena such as volcanoes, storms, earthquakes etc. also cause major changes in water chemistry and the ecological status of water, these are not deemed to be pollution. Water pollution has many causes and characteristics. Humans and other farmed organisms produce bodily wastes which enter rivers, lakes, oceans and other surface waters. These wastes increase the solids suspended in the water (turbidity), they can increase the concentration of bacteria and viruses leading to potential health impacts. Increases in nutrient loading may lead to eutrophication). Organic wastes such as sewage and farm waste impose high oxygen demands on the receiving water leading to oxygen depletion with potentially severe impacts on the whole eco-system. Industries discharge a variety of pollutants in their wastewater including heavy metals, organic toxins, oils, nutrients, and solids. Discharges can also have thermal effects, especially those form power stations, and these too reduce the available oxygen. Silt-bearing runoff from many activities including construction sites , forestry and farms can inhibit the penetration of sunlight through the water column restricting photosynthesis and causing blanketing of the lake or river bed which in turns damages the ecology.

Pollutants in water include of a wide spectrum of chemicals, pathogens, and physical chemistry or sensory changes. Many of the chemical substances are toxic or even carcinogenic. Pathogens can obviously induce disease in either human or animal hosts. Alteration of water's physical chemistry include acidity, conductivity and temperature. excessive nutrient loading (eutrophication). Even many of the municipal water supplies in developed countries can present health risks. In the U.S. beginning in 1972 stringent federal laws were enacted setting specific discharge limitations.

Contents

1 Sources of water pollution
2 Contaminants
3 Transport and chemical reactions of water pollutants
4 Regulatory framework
5 Bibliography
6 See also
7 External links

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Sources of water pollution

The causes of water pollution can be divided into two groups: anthropogenic sources of pollution are those due to human acts, sources include:

industrial discharge of chemical wastes and byproducts
discharge of poorly-treated or untreated sewage
runoff contining pesticides and herbicides
runoff containing spilled petroleum products
runoff from construction sites, farms, or paved and other impervious surfaces e.g. silt
discharge of contaminated and/or heated water used for industrial processes
acid rain caused by industrial discharge of sulfur dioxide (by burning high-sulfur fossil fuels)
excess nutrients added by runoff containing detergents or fertilizers

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Contaminants

Pumping of highly toxic (dark black) sludge, much seeps back into the ocean in the form of tiny particles

Contaminants may include organic and inorganic substances.

Some salient organic water pollutants are:

pesticides and herbicides, a huge range of organohalide and other chemicals
bacteria, often is from sewage or livestock operations;
food processing waste, including pathogens
tree and brush debris from logging operations

Some inorganic water pollutants include:

heavy metals including acid mine drainage
acidity caused by industrial discharges (especially sulfur dioxide from power plants)
chemical waste as industrial byproducts
fertilizers, in runoff from agriculture including nitrates and phosphates
silt in stormwater runoff from construction sites or cleared land

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Transport and chemical reactions of water pollutants

Most water pollutants are eventually carried by the rivers into the oceans. In some areas of the world the influence can be traced hundred miles from the mouth. Indicator filter feeding species such as copepods are used to study pollutant fates in the New York Bight, for example. The highest toxin loads are not directly at the mouth of the Hudson River, but 100 kilometers south, since several days are required for incorporation into planktonic tissue. The Hudson discharge flows south along the coast due to the coriolis force. Further south then are areas of oxygen depletion, caused by chemicals using up oxygen and by algae blooms, caused by excess nutrients from algal cell death and decomposotion. Fish and shellfish kills have been reported, because toxins climb the foodchain afer small fish consume copepods, then large fish eat smaller fish, etc. Each step up the food chain concentrates certain toxins like heavy metals and DDT by approximately a factor of ten.

Many chemicals undergo reactive decay or change especially over long periods of time in groundwater reservoirs. A noteworthy class of such chemicals are the chlorinated hydrocarbons such as trichloroethylene (used in industrial metal degreasing) and tetrachloroethylene used in the dry cleaning industry. Both of these chemicals, which are carcinogens themselves, undergo partial decomposition reactions leading to new hazardous chemicals.

Groundwater pollution is much more difficult to abate than surface pollution because groundwater can move great distances through unseen aquifers. Non-porous aquifers such as clays partially purify water of bacteria by simple filtration (adsorption and absorption), dilution, and, in some cases, chemical reactions and biological activity: however, in some cases, the pollutants merely transform to soil contaminants. Groundwater that moves through cracks and caverns is not filtered and can be transported as easily as surface water. In fact this can be aggravated by the human tendency to use natural sinkholes in seldomly occuring areas of Karst topography.

There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. Some of these secondary impacts are:

Silt bearing runoff from can inhibit the penetration of sunlight through the water column, hampering Photosynthesis in aquatic plants.
Thermal pollution can induce fish kills and invasion by new thermophyllic species

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Regulatory framework

In the UK there are common law rights to protect the passage of water across land unfettered in either quality of quantity. Criminal laws dating back to the 16th century excercised some control over water pollution but it was not until the River (Prevention of pollution )Acts 1951 - 1961 were enacted that any systematic control over water pollutuion was established. These laws were strengthened and extended in the Control of Pollution Act 1984 which has since been updated and modified by a series of further acts.

In the USA Growing public awareness and concern for controlling water pollution led to enactment of the Federal Water Pollution Control Act Amendments of 1972. As amended in 1977, this law became commonly known as the Clean Water Act. The Act established the basic mechanisms for regulating contaminant discharge. It established the authority for EPA to implement wastewater standards for industry. The Clean Water Act also continued requirements to set water quality standards for all contaminants in surface waters. Further amplification of the Act continued including the enactment of the Great Lakes Legacy Act of 2002 (Public Law 107-303, November 27, 2002).

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Bibliography

C. Michael Hogan and Leda C. Patmore, Computer simulation of pesticide runoff in five instrumented watersheds, Environmental Protection Agency, Southeast Water Lab, Athens, Georgia, prepared by ESL Inc, Sunnyvale, Ca., (1972)

David H.F. Liu, Bela G. Liptak, and Paul A. Bouis, Groundwater and Surface Water Pollution, CRC Press (2000) ISBN 1-56670-511-8

Great Lakes Legacy Act of 2002 Public Law 107-303, November 27, 2002

P.D. Abel, Water Pollution Biology, Taylor & Francis (1996) ISBN 0-7484-0661-1

U.S. Clean Water Act of 1972

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See also

Environmental pollution
Pollution
Soil contamination
Water quality
Water resources
Wastewater quality indicators
Marine pollution
Oxygen depletion
Environmental engineering
Thermal pollution

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External links

U.S. Environmental Protection Agency Homepage
Read Congressional Research Service (CRS) Reports regarding Water Pollution
Kentucky Division of Water Homepage
Natural Resources Defense Council (NRDC): overviews, news and reports on water pollution
Troubled Waters: Episode and web site from National Geographic/PBS's "Strange Days on Planet Earth"
South Australian EPA Homepage

Retrieved from "http://en.wikipedia.org/wiki/Water_pollution"

Categories: Wikipedia cleanup | Environmental science | Pollution | Water | Hydrology

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This page was last modified 23:00, 2 March 2006.
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