Welfare Effects - Acid Rain

"Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry. Acid deposition occurs when emissions of sulfur dioxide and nitrogen oxides in the atmosphere react with water, oxygen, and oxidants to form acidic compounds. These compounds fall to the earth in either dry form (gas and particles) or wet form (rain, snow, and fog). In the United States, about 63 percent of annual SOx emissions and 22 percent of NOx emissions are produced by burning fossil fuels for electricity generation (Latest Findings on National Air Quality, 2002). Because it typically takes days to weeks for atmospheric SO2 and NOx to be converted to acids and deposited on the earth's surface, acid deposition occurs in a multistate scale hundreds of miles away from its sources.

Acidity is measured in terms of pH on a logarithmic scale from 1.0 to 14.0. A pH of 1.0 indicates high acidity, whereas a pH of 14.0 indicates high alkalinity; a pH of 7.0 indicates a neutral solution. Precipitation falling through a "clean" atmosphere is normally somewhat acidic, with a pH of about 5.6. Acid rain, however, can have a pH values below 4.0.

Figure:Acid rain formation

In the environment, acid deposition causes soil and water bodies to acidify (making the water unsuitable for some fish and other wildlife) and damages some trees, particularly at high elevations. It also speeds the decay of buildings, statues, and sculptures that are part of our national heritage. The nitrogen portion of acid deposition contributes to eutrophication (oxygen depletion) of water bodies, the symptoms of which include algal blooms (some of which may be toxic), fish kills, and loss of plant and animal diversity. These ecological changes impact human populations by changing the availability of seafood and creating a risk of consuming contaminated fish or shellfish, reducing our ability to use and enjoy our coastal ecosystems, and causing economic impact on people who rely on healthy coastal ecosystems, such as fishermen and those who cater to tourists.

More information on acid rain can be found at: http://www.epa.gov/air/acidrain.html