In a pristine lake basin 9,300 feet high in the Sierra Nevada, scientists are manning an early warning post, waiting for the first signs that acid pollution is damaging California's environment.
The Emerald Lake watershed, part of the wilderness in Sequoia National Park, is the site of the most comprehensive set of studies being conducted under the sponsorship of the California Air Resources Board's acid rain research program.
For nearly four years, scientists have probed every aspect of the lake basin: measuring how much acid rain, snow and dust it receives, and how the acid affects trees, other plants, soils, stream and lake sediments, and fish and other marine life.
Researchers are watching Emerald Lake and other sections of the Sierra carefully because the mountain range is where acid pollution damage is likely to show up first in California.
Sierra lakes, like those in New York state's Adirondack Mountains, sit in granite, which lacks the minerals needed to neutralize acid and thus resist acid pollution.
So far, experts agree that there are no obvious signs of dying fish or other environmental damage from acid pollution in California, which hasn't been exposed to industrial pollutants as long as Europe and eastern North America.
"We've only been exposing the environment to this for 50 or 60 years in this state, and we don't know what the long-term ecological implications are," said Michael Hoffman, a California Institute of Technology researcher. "My gut feeling is it isn't good."
The Air Resources Board's last annual acid rain report said potential environmental problems include acidification of lakes and streams, damage to crops, forests, grasslands and chaparral, and damage to man-made materials and structures.
Acidity can render lakes and streams lifeless by making them inhospitable to microorganisms, salamanders, frogs and fish, harming the creatures' ability to reproduce and develop.
Acid pollution theoretically may directly damage needles and leaves on trees and other plants, interfere with the conversion of nitrogen in soil to a form usable by plants, leach needed nutrients from the soil and release toxic metals from soil so they poison plants.
Chronic acidification of lakes and streams has been documented in northern Europe, Canada and the northeastern United States, many scientists and environmentalists say. And there is clear evidence that trees in Europe, Canada and the East have suffered declines in health and growth.
But the link between acid pollution and environmental damage still is disputed intensely.
A report issued in September by the Reagan Administration's National Acid Precipitation Assessment Program, which coordinates federal acid rain research, concluded there is little evidence that acid pollution has caused significant harm to U.S. lakes and streams.
The report drew protest from the Canadian government, environmental groups and many scientists. One Canadian official termed it "voodoo science" aimed at stalling cleanup action. The Natural Resources Defense Council called it "political proganda," but the report's chief author said he resented such criticism as an attack on his integrity.
"Although the effects hypothesized to be associated with acid deposition include those on soils, forests, crops and (man-made) materials, conclusive evidence exists only for injury to aquatic ecosystems," said an earlier report in an American Chemical Society magazine.
The National Academy of Sciences' National Research Council reported in 1986 that acid rain has damaged lakes in the Northeast and is associated with declines in fish populations, but "the potential effects of acid rain on forests remain unresolved."
The Air Resources Board's last annual report said: "A positive link has not yet been established between acid deposition and forest tree damage."
George Hidy, now a vice president of the Electric Power Research Institute, reviewed scientific studies of acid-related environmental damage in his former job as the head of the University of Nevada's Desert Research Institute.
The reviews, conducted on behalf of utilities and oil and gas producers, found "no evidence of any effects of acid deposition in the West to forests or to lakes, and at the current deposition rates, the study group did not expect any effects, based on available information," Hidy said.
But an Environmental Protection Agency study released this year concluded that although lakes in the West have yet to be spoiled by acid pollution, about two-thirds of Western lakes may be susceptible in the long run, and the greatest number are in California.
Pollution in East
An earlier EPA study found 10% of lakes in the East were polluted by acid, and half were sensitive to acidity.
Air Resources Board-sponsored studies at Emerald Lake and elsewhere already show that lakes in the Sierra Nevada, northwest California's Trinity Alps and the southern Cascade Mountains have a low acid-neutralizing capacity and are vulnerable to acid pollution.
"We don't know how soon the (protective) alkalinity will be gone, but we know it's being diminished," said John White, a consultant who lobbies on acid rain issues for the Sierra Club. "We know from the East that once it's gone it's gone, and you've acidified these lakes."
Emerald Lake, which is typical of Sierra lakes, completely loses its acid-neutralizing ability temporarily due to a large release of acid during the spring snowmelt and summer storms, state-sponsored research shows.
Air pollution damage to California's forests was first noted in mountains surrounding the Los Angeles Basin, where ozone damage to conifer needles was discovered in 1980. Ozone damage in the Sierra was detected in 1984 in trees in Sequoia and Yosemite national parks. Sulfur dioxide damage also has been noted.
Scientists at Cornell University, North Carolina State University and elsewhere agree the only pollutant conclusively linked to forest damage is ozone, the main pollutant in photochemical smog.
Hoffman said he fears that, like ozone, acid pollution from the San Joaquin Valley that wafts into the Sierra damages trees.
But Hidy insisted: "The only evidence of forest damage in the Sierra is associated with ozone."
White said there is evidence that acid pollution may worsen ozone damage to trees.
Ozone also may be a bigger threat than acid pollution to California's annual $14-billion agricultural industry.
Air pollution has been blamed for reducing yields of some San Joaquin Valley crops by up to 20%. Scientists say ozone is the main culprit, but they believe acid contributes to the damage, said Air Resources Board spokesman Bill Sessa.
EPA research shows that most crops are not harmed when farm soil receives acid rain with a pH range of 4.0 to 4.5, the average level of acidity in highly polluted areas of the East.
"The general consensus among researchers is that acidic rain at current levels probably does not appreciably affect yields of most crops," said the Air Resources Board's annual report.
Hard to Measure
But the board fears that California crops may be damaged by acid fog or dry acid dust, which is difficult to measure.
Board-sponsored research shows that both ozone and very acidic fog with a pH measurement of 1.6--acidity that sometimes occurs in foggy coastal areas--reduce the growth and yield of economically important California crops, including tomatoes, strawberries, alfalfa, green peppers and celery.
"The effects one sees are really at quite high acidities," said Jim Pitts, director of the Statewide Air Pollution Research Center at the University of California, Riverside.
Holmes said acid pollution may be a particular threat to grazing lands located on shallow soils.
Damage to Buildings
Man-made structures also suffer from acid pollution. A study conducted for the EPA and other agencies concluded that acid damage to buildings in the United States costs $3.5 billion to $6 billion a year.
Another study estimated that airborne acid, which erodes and soils painted surfaces, increases annual maintenance costs by $50 million a year in Los Angeles, Orange, San Bernardino and Riverside counties. That doesn't include damage to other materials, such as concrete and steel.
"Damage to materials from air pollution and acid deposition may occur in a variety of forms, including erosion and discoloration of paints, cracking of rubber, corrosion of metals, soiling and decay of building stone and concrete," the Air Resources Board's annual report said. "Major economic impacts are increased costs of maintenance, repair and replacement."
The major question is how much of such damage is due to acid and how much is caused by other air pollutants, the report said.