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Water Pollution |
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Water pollution is a large set of adverse
effects upon water bodies (lakes, rivers, oceans, groundwater) caused by human activities.
Although natural phenomena such as volcanoes, storms, earthquakes etc. also cause major changes
in water quality 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 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 produce waterborne diseases
in either human or animal hosts. Alteration of water's physical chemistry include acidity, conductivity, temperature,
and excessive nutrient loading (eutrophication). Even many of the municipal water supplies in developed countries can
present health risks. In the U.S.in 1972 stringent federal laws were enacted setting specific discharge limitations.
Water pollution is a serious problem in the global context. It has been suggested that it is the leading
worldwide cause of death and disease, and that it accounts for the deaths of more than 14,000 people daily.
Principal sources of water pollution are:
- industrial discharge of chemical wastes and byproducts
- discharge of poorly-treated or untreated sewage
- surface runoff containing pesticides
- slash and burn farming practice, which is often an element within shifting cultivation agricultural systems
- surface runoff containing spilled petroleum products
- surface 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
- underground storage tank leakage, leading to soil contamination, thence aquifer contamination.
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