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Types of pollution
 
Environmental Pollution
Types of pollution
Air pollution
Water pollution
Soil pollution
Controlling pollution
Government action
Scientific efforts
Business and industry
Agriculture
Environmental organizations
History
The growth of pollution
Progress in controlling pollution
Current environmental issues
 
The Clean Development Mechanism
Global warming
Reducing emissions (REDD)
Swine Influenza
Cholesterol
Heart Attack
 

Types of pollution

The chief types of environmental pollution include air pollution, water pollution, soil pollution, pollution caused by solid waste and hazardous waste, and noise pollution.

Water pollution

Water pollution is the contamination of water by sewage, toxic chemicals, metals, oils, or other substances. It can affect such surface waters as rivers, lakes, and oceans, as well as the water beneath Earth's surface, called ground water. Water pollution can harm many species of plants and animals. According to the World Health Organization, nearly one-sixth of the world's people have no access to safe drinking water.

In a healthy water system, a cycle of natural processes turns wastes into useful or harmless substances. The cycle begins when organisms called aerobic bacteria use the oxygen dissolved in water to digest wastes. This digestion process releases nitrates, phosphates, and other nutrients (chemical substances that living things need for growth). Algae and aquatic green plants absorb these nutrients. Microscopic animals called zooplankton eat the algae, and fish eat the zooplankton. The fish, in turn, may be eaten by larger fish, birds, or other animals. These larger animals produce body wastes and eventually die. Bacteria break down dead animals and animal wastes, and the cycle begins again.


Water pollution comes from businesses, farms, homes, industries, and other sources. It includes sewage, industrial chemicals, agricultural chemicals, and livestock wastes. Water pollution occurs when people put so much waste into a water system that its natural cleansing processes cannot function properly. Some waste, such as oil, industrial acids, or farm pesticides, poisons aquatic plants and animals. Other waste, such as phosphate detergents, chemical fertilizers, and animal manure, pollutes by supplying excess nutrients for aquatic life. This pollution process is called eutrophication. It begins when large amounts of nutrients flow into a water system. These nutrients stimulate excessive growth of algae. As more algae grow, more also die. Bacteria in the water use up large amounts of oxygen consuming the excess dead algae. The oxygen level of the water then drops, causing many aquatic plants and animals to die.

Another form of water pollution is the clean but heated water discharged by power plants into waterways. This heated water, called thermal pollution, harms fish and aquatic plants by reducing the amount of oxygen in the water. It may also affect fish that rely on seasonal temperature changes to locate their breeding grounds. Chemical and oil spills can cause devastating water pollution that kills water birds, shellfish, and other wildlife.

Some water pollution occurs when there is improper separation of sewer wastewater from clean drinking water. In parts of the world that lack modern sewage treatment plants, water carrying human waste can flow into drinking water supplies. Disease-carrying bacteria in the waste can then contaminate the drinking water and cause such illnesses as cholera and dysentery. In areas with good sanitation, most human waste flows through underground pipes to special treatment plants that kill the harmful bacteria and remove the solid waste.

Water pollution also occurs when chemicals seep through the ground and enter aquifers, areas where ground water is stored in porous rock. Such pollution is a concern because aquifers supply much of the drinking water and water for farms in some areas. The lack of oxygen in aquifers inhibits bacteria from breaking down contaminants, and the isolation of aquifers underground makes it difficult to locate and remove pollutants from them. Chemicals that enter ground water can remain there for long periods and continue to contaminate local water supplies.


Contributor:
Marian R. Chertow, M.P.P.M., Director, Industrial Environmental Management Program, Yale School of Forestry and Environmental Studies.
Source :
World Book 2005