Water Pollution: Part 2

Industry

Many industries dump organic and inorganic wastes into bodies of water. These may be acids, highly toxic minerals, or, in the case of petroleum refineries, toxic organic chemicals. The nuclear power industry has caused some water pollution when radioactive material has seeped from tanks containing nuclear wastes. Acid rain, a by-product of emissions from factories, power plants, and motors vehicles, has affected the water quality of thousands of lakes and streams.

Mining

Surface mining for coal, iron, copper, gold, and other substances contributes to contamination of the water supply through the wastes it generates. Rainwater reacts with the wastes, and dissolved minerals seep into nearby water bodies. In addition to altering the quality of the water, contaminants affect plant and animal life. Each year, for example, thousands of animals and migratory birds die in such western states as Arizona, Nevada, and California after drinking cyanide-laced waters at gold mines.

Municipalities

Human waste, detergents, and trash are the kinds of pollutants associated with towns and cities. Sewage can be a major water pollutant, depending on how well it is treated with chemical disinfectants or filters before being discharged. Raw, untreated human waste contains viruses responsible for dysentery, hepatitis, spinal meningitis and other diseases. More than 25% of all sewage in the U.S. flows untreated into rivers, lakes, and oceans. The figure is even higher in Canada, about 40%.

Urban Drainage

Water runoff from urban areas contains contaminants from insecticides, animal droppings, litter, vehicle drippings, and the like. The use of detergent has increased the phosphorous content of rivers, and salt (used for deicing roads) increases the chloride content of runoff. Because the sources of pollution are so varied, the water supply in any single area is often affected by diverse pollutants. Contaminated drinking-water wells have been found in more than half of the states. Thousands of wells that tap aquifers have been closed in such states as New York, New Jersey, Massachusetts, and California. The pollution of aquifers is particularly troublesome because we depend on them for about half of our drinking water – yet unlike surface waters, groundwater lacks natural cleansing properties; it can remain contaminated for centuries.