Acid from the Skies

Corrosive rain has become an insidious menace

Just a little breeze with some smoke in its eye,

What have they done to the rain ? --Malvina Reynolds

Already it has killed off the fish in about a hundred lakes in New York's Adirondack wilderness. It has pelted the slopes of the Rockies, and has already affected Scandinavia and much of industrialized Western Europe and Japan. It is a newly recognized and increasingly harmful kind of pollution, invisible and insidious: acid rain, a corrosive precipitation that actually consists of weak solutions of sulfuric and nitric acids.

Last November 35 nations, including the U.S., gathered in Geneva and signed a pact pledging to work together against this skyborne peril. President Carter has authorized a $10 million annual outlay for a ten-year research program on acid rain, which he considers one of the two gravest environmental threats of the decade (the other: increasing levels of carbon dioxide in the atmosphere from the burning of fossil fuels).

Acid precipitation is apparently caused largely by sulfur dioxide emissions from coal-burning power plants, smelters and factories. To a lesser extent, nitrogen oxides from car exhausts and industry contribute to the problem. Rising high into the sky and borne hundreds of miles by winds, these chemicals mix and react with water vapor to form sulfuric and nitric acids. The acids then fall to earth in the form of rain or snow that can damage anything from monuments to living organisms. After a number of such rain showers or highly acidic snow melts, a lake's pH* can plunge low enough to impair the egg-producing ability of fish. Decomposition of organic matter slows, probably because of a loss of scavenging microorganisms. The number of plankton falls off sharply, depleting a vital link in the food chain. Finally, the water appears blue, clear--and virtually lifeless.

The ill effects spread beyond the lakes. In some areas, humans may also be affected. In the Lac la Croix lake system of Ontario, where the Ojibway Indians fish for their livelihood, catches are showing high levels of mercury. Reason: the toxic metal, ordinarily concentrated in sediment, changes into an organic form, methyl mercury, in acid water and is then easily absorbed by the fish. While the threat to plants is not as well understood, acid rain can eat away at leaves, leach nutrients from the soil, interfere with photosynthesis, and affect the nitrogen-fixing capabilities of such plants as peas and soybeans. Scandinavian scientists claim the rain has caused a 15% reduction in timber growth. It can also corrode stone statues, limestone buildings and metal rooftops. In the past two decades, Athens' Parthenon and Rome's Colosseum have deteriorated severely; the prime suspect is acid rain. In the U.S. it may cause as much as $2 billion each year in structural damage.

Paradoxically, one tactic in the fight against air pollution has contributed to the increase in acid rain. To keep the air clean in the immediate neighborhoods of factories, industry has been building ever taller smokestacks. These belch gases that are out of sight--and out of mind--for local communities, but not for those downwind. The farther the gases go, the more time they have to combine with moisture and form acids. Indeed, scientists estimate that the world's tallest stack, rising 1,250 ft. above a copper-nickel smelter in Sudbury, Ont., accounts for 1% of all sulfur emissions in the world, including those from volcanoes. All told, Canadian industry and the winds send about half a million tons of these emissions south to the U.S. every year.

But Canada gets more than it gives. Some 2 million tons annually blow north across the border from the U.S., mostly from the industrial Ohio River Valley, which is also thought to be the main source of the Northeast's acid-rain problem. In Europe, says Svante Oden, a Swedish soil scientist, acid rain is equivalent to a "chemical war." Scandinavians claim they are being "bombed" by British and German factories, and similar charges have been exchanged by France and West Germany.

Written before any widespread alarm about acid precipitation, the U.S. Clean Air Act of 1970 gives states a liberal hand in controlling their own emissions to meet federal air quality standards. But it does not assign any responsibility for blights one state may inflict on another. The result has been a see-no-evil attitude that may well require more federal intervention. Also, the 1970 act sets standards only for "ambient," or ground-level air quality; acid rain is formed by high-floating emissions.

In some regions, nature itself buffers the effects of damaging rain; alkaline soils and rocks in the vicinity of the lake help neutralize the acidic water. But when man has tried to duplicate the process by spreading lime on and around endangered lakes, the task has proved expensive and only a temporary palliative.

Taking aim at the source of the trouble, the EPA is requiring the installation of scrubbers that remove up to 90% of sulfur emissions at all new coal-fired power plants. But older plants are not covered by the new law, and the problem is likely to worsen as the country turns increasingly to its vaunted ace in the energy hole, coal. "Washing" high-sulfur coal can help. This process involves crushing the coal, then separating out pyrite, an iron-sulfur compound. Because ash, dirt and rock are removed at the same time, washing also makes the coal more economical to ship and less damaging to utility boilers. Still, the expense of these measures is staggering. By one estimate, just to cut sulfur dioxide emissions by 50% in the Northeastern U.S. alone would cost up to $7 billion annually.

Yet even at such prices a solution may be a bargain. For as ecologists point out, doing nothing about acid rain now could mean nightmarish environmental costs in the future.

*pH is a scale, ranging from 0 to 14, for measuring acidity or alkalinity. A chemically neutral solution is denoted by 7, increasing acidity by lower numbers (each one representing a tenfold increase), and rising alkalinity by numbers greater than 7. Rain or snow has a natural pH around 5.6, resulting mainly from atmospheric carbon dioxide, which produces a weak solution of carbonic acid.

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