
The commonly used terms acid rain and acid precipitation describe specific forms of a type of pollution described generally as acid deposition.
Harmful gases that rise into the air mix with cloud moisture, sunlight, and oxidants. There they chemically combine into dilute sulfuric and nitric acids, which fall back to the earth. This is acid deposition. The major contributing pollutantssulfur dioxide and nitrogen oxidescome from factories, power plants, automobile exhaust, chemical fertilizers, and other sources. In concentrations sometimes more acidic than lemon juice, the pollutants reach the earth in rain, snow, hail, sleet, or fog. Dry acidic particles also fall from the atmosphere. Because wind can carry gases and moisture for hundreds of miles, even areas far away from the source bear the effects of acid deposition.
Many scientists believe that acid deposition contributes to deforestation and soil degradation. It is known to dramatically accelerate the deterioration of buildings, including landmarks such as the Acropolis in Athens, the Taj Mahal in India, and the Statue of Liberty in New York City. Though much of the world is affected by acid deposition, its worst consequences are found in parts of Eastern Europe.
Acid deposition may threaten human health, and it has taken a toll on wildlife. Some of the most noticeable effects are on aquatic life including fish, amphibians, and microscopic organisms that play an important role in water ecosystems. Many lakes, streams, and rivers have suffered profound loss of life. The waters of tens of thousands of Scandinavian lakes are now unnaturally clear due to this phenomenon, the responsible contaminating acids carried there by prevailing winds from far-flung European locations. Hundreds of lakes in New Yorks Adirondack Mountains are sterile. Because species are interdependent, the loss of one can trigger the death of many others.
In the U.S., some progress has been made through environmental legislation. Some international agreements have placed limits on the production of offending pollutants. In some places, the introduction of cleaner coal-burning technologies has eased environmental stress. Though much has been learned about this extremely complex problem, many answers still elude science.
The following organizations are among those working toward solutions to the acid deposition problem:
Center for Clean Air
444 North Capitol Street N.W., #602
Washington, D.C. 20001
telephone +1 202 624 7709
The Acid Rain Foundation
1509 Varsity Drive
Raleigh, North Carolina 27606
telephone +1 919 515 5290
Environmental Protection Agency, Atmospheric Programs
401 M Street S.W.
Washington, D.C. 20460
telephone +1 202 233 9150
National Acid Precipitation Assessment Program
1110 Vermont Avenue N.W., # 810
Washington, D.C. 20005
telephone +1 202 296 1002
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