Acid Rain Down, but Many Lakes Not Recovering

Acid precipitation in the U.S. continues to decline, but many lakes and streams remain acidified, says a report released last week by the President's National Science & Technology Council. The report analyzes the results of the national program, established in 1990, to control acid rain by requiring fossil-fuel-fired power plants to curb emissions of sulfur dioxide and nitrogen oxides. These pollutants are linked to acidification of surface waters as well as to air pollution. The report, required under the Clean Air Act, says that in 2002, SO₂ emissions in the U.S. were 35% lower and NO_x releases were 33% lower than they were in 1990. In response, some lakes and streams in the Northeast are beginning to see their pH rise, the report says. It adds, however, that "recovery from the effects of acidification is not possible for many areas that continue to be exposed to acid deposition." Further cuts in SO₂ and NO_x from the power sector and from vehicles are needed to reduce the number of acidic lakes and streams in many parts of the U.S., it concludes. The report is available at www.al.noaa.gov/AQRS/reports/napapreport05.pdf.