WASHINGTON — Acid rainfall in the western United States, while still far less severe than in the East, poses an "apparent" threat of environmental damage to wide stretches of sensitive wilderness and watershed lands, a new analysis of pollution and geological data from Western states concludes.
The study, to be released today by the Washington-based World Resources Institute, says that California's Sierra Nevada, Washington's Cascades and the Colorado Rockies are especially vulnerable because those mountain lands are poorly suited to buffering the effects of acid precipitation already falling there.
"The risk of damage, which could not have been appreciated a few years ago because few reports of acidic deposition in sensitive Western ecosystems were available, is now apparent," the report states. "How long chemical and environmental changes might take, however, is still not well understood."
Acid precipitation is created when sulfur and nitrogen oxides from auto and industrial pollution react with water in the atmosphere. In the West, where there is generally less rain than in the East, much precipitation falls as snow or as nearly invisible "dry" droplets.
Scientists generally agree that the phenomenon has reduced or wiped out aquatic life in some northeastern U.S. lakes and streams and that it may be linked to dieback in mountain forests across the East.
Likened to Northeast
A co-author of the study, UC Berkeley scientist John Harte, likened the West's acid rain threat to that which confronted Northeastern states a decade or two ago, before damage became obvious.
"As yet, we have seen no evidence of biological damage," Harte said. "But we know from numerous studies in the East that as these events increase . . . and the buffering capacity of soils and lakes continues to decline, biological damage is very likely to occur."
Chemical changes already evident in some Western lakes "are the same as people noticed in the East before forests began dying," said Mohamed El-Ashry, another of the study's authors. "That's why we're raising the red flag."
The institute's 18-month analysis combined the existing sketchy data on Western acid precipitation with weather and geological studies of the region. Among other findings, the study concludes that Western precipitation is only 25% to 50% as acidic as rain and snowfall in many Eastern states.
Effects May Be Increased
However, the report states, environmental effects may be magnified in the West because "dry" precipitation and snow tend to accumulate over long periods, triggering highly acidic "pulses" when the snow melts or rain washes the dry deposits away.
Moreover, the mountain regions where precipitation is most acidic have thin soils, steep slopes and granite bedrock--conditions that reduce the ability of the soil to neutralize acid deposits.
Federal scientists claim to have documented a 15-year rise in the acidity of lakes and streams on the western slope of the Colorado Rockies, and there is "solid evidence" of pollution-caused acid rain in the Cascade Mountains east of Seattle and Tacoma, Wash., the report states.
The study points to California as a prime source of acid-rain components, largely because of the state's autos and oil refineries. California produces 38% of the West's nitrogen oxides and 16% of its sulfur pollution, and Harte said that Los Angeles smog is a likely contributor to acid rainfall as far away as the Rockies.
Smelters a Source
Another major source of sulfur pollution--Western-state copper smelters--may decline in importance as federal pollution curbs take effect in 1988, the report states. But the construction of new smelters in Mexico and an expected increase in the burning of fuels by electric-power plants are likely to more than make up the difference.
The institute's report urges Western states to counter acid-rain threats by enacting mass-transportation plans, locating heavy industries in areas where they will not contribute to existing acid-rain patterns and studying new controls on power-plant pollution.
In addition, the study urges federal officials to "urgently" negotiate a treaty with Mexico to impose pollution controls on the new smelters there.