What's the source of acid rain?

What's the source of acid rain?

When President Carter set up the National Acid Precipitation Assessment Program (NAPAP) in 1980 (SN: 2/24/90, p.119), researchers lacked a reliable inventory assessing annual emissions of the primary pollutants responsible for acid rain. Even today, most emissions from human activities are estimated, not measured, using formulas for standard power plants and vehicles, notes Marylynn Placet, a Washington, D.C.-based policy analyst with Argonne (Ill.) National Laboratory. Nevertheless, NAPAP has now compiled "a fairly comprehensive and accurate picture" of those emission levels, she says.

The new repor, coauthored by Placet, indicates than human activities in 1985 spewed 23.1 million tons of sulfur dioxide, 20.5 million tons of nitrogen oxides and 22.1 million tons of volatile organic compounds into U.S. air. That's a drop from 1970 of roughly 30 percent for sulfur dioxide and volatile organic compounds, and of 8 to 16 percent for nitrogen oxides. Large facilities, mainly electric power plants, became the major sulfur dioxide source only after 1960. Today, they produce more than 75 percent of that pollutant, thought they contribute only 27 and 1 percent of the nitrogen oxides and volatile organic compounds, respectively. The Northeast emits more than 50 percent of the nation's sulfur dioxide, 39 percent of the nitrogen oxides and 40 percent of the volatile organic compounds.