University Park, Pa. -- Acid rain levels have decreased as much as 20 percent over a large region of the Eastern U.S. thanks to the Clean Air Act of 1990, according to a Penn State researcher.
"Pennsylvania has long been recognized as the acid rain capital of the country," says James A. Lynch, professor of forest hydrology, school of forest resources. "The pollutants that cause acid rain come from local sources and sources located in the Midwest and affect a wide region up into New England.
"However, since implementation of phase one of title VI of the Clean Air Act of 1990, acid rain concentrations in the North Eastern U.S. have decreased by as much as 20 percent," Lynch recently told attendees at the Pennsylvania Acidic Deposition Conference, University Park, Pa.
Acid rain is caused by sulfur dioxide and nitrogen oxides produced when fuels burn. The source of most sulfur dioxide is high-sulfur coal burned in power plants. Controlling this source of sulfur dioxide production can have a major impact on acid rain in Pennsylvania and other regions of the Northeast.
Unfortunately, only 30 percent of the nitrogen oxides causing acid rain come from power production. Automobiles generate another 30 percent and the agricultural sector contributes an additional 25 to 30 percent. Lightening strikes and biological processes produce the remaining nitrogen naturally. Consequently, it is much more difficult to control and regulate nitrogen oxides.
In 1995, Phase one of the Clean Air Act Amendments of 1990 took effect for 110 electrical utilities. Most of these power plants were in the Eastern U.S. with a few plants located west of the Mississippi River. The act specified a reduction of sulfur dioxide emissions of 10 million tons, based on 1980 levels. Reduction at the 110 utilities affected by phase one were set at 2.3 million tons.