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.