Study Blames Acid Rain for 75% of Acidic Lakes

A nationwide study of thousands of acidic lakes and streams has identified acid rain as the cause of the acidity in 75% of the lakes and 47% of the streams, researchers said Thursday.

Acid conditions in the remainder of lakes and streams were the result of natural acidity in the watershed or acidic draining from coal mines, they reported in Science magazine.

Acid rain describes industrial pollution--such as sulfuric acid from coal-fired power plants--carried long distances in the atmosphere before returning to earth in rain, snow or soot.

The result can be crystal-clear lakes where all the fish have died, a blow to tourism in the northeastern United States and Canada, where the effects are concentrated.

But natural processes can also make a lake or stream acidic, and some people have argued that the role of acid rain has been overstated by those who urged expensive action to curtail it. Last year’s Clean Air Act will require electric utilities and other industries to cut their sulfur dioxide emissions roughly in half.

Lawrence A. Baker, a scientist at the University of Minnesota Resources Research Center who led the study, said the researchers considered various evidence but relied most heavily on a chemical analysis of the acidic water to identify the source of the acid.

Their work used data from a survey by the Environmental Protection Agency of 1,180 lakes and 4,670 streams in what EPA determined to be acid-sensitive areas of the United States.

The area where lakes were most likely to have been affected by acid rain was the Adirondack mountains of Upstate New York. Baker said the researchers were surprised to find streams in the high-elevation forests of Virginia, Pennsylvania and West Virginia had also been affected by acid rain.

The study found that 26% of the streams in the EPA survey had been turned acidic by drainage from mine tailings. They were primarily in the mid-Atlantic coal-mining region.

About one-fourth of the lakes and one-fourth of the streams were naturally acidic.