Acid Rain: Poison from Above

As important as water conservation efforts are, acid rain produced by the burning of fossil fuels could render them moot.

| January/February 1983

  • Anne and Paul Ehrlich
    Professors Anne and Paul Ehrlich research and write extensively on ecological issues.
  • acid rain rock sensitivity map
    This map of the U.S. shows the sensitivity of the country's rock strata to acid rain.
    Illustration by MOTHER EARTH NEWS Staff

  • Anne and Paul Ehrlich
  • acid rain rock sensitivity map

In our last column we noted that even strong conservation measures, strict control of localized pollution sources, and the protection of recharge areas would probably not be adequate to safeguard America's ground-water resources. One reason for this, of course, is that the demands of population and economic growth could easily keep withdrawal rates higher than recharge rates in spite of conservation and watershed preservation. A second factor is the potential for pollution originating in the rain itself.

Until recently, the notion of rain as a source of pollution seemed preposterous, but humanity has steadily increased its use of fossil fuels. Among the products of such combustion are oxides of sulfur and nitrogen, which are spewed into the atmosphere by automobile exhausts and factory/powerplant smokestacks. There, the oxides take part in a variety of chemical reactions, producing (among other things) sulfuric and nitric acids.

These potent acids, mixed with rainwater, are now descending upon us as acid rain. Over vast areas of North America, Europe, and Asia, rain has become 10 to 1,000 times more acid than normal. Until recently, the record was held by Pitlochry, Scotland, where in 1974 the rain was as acid as vinegar! In 1981, however, this dubious first-place award was captured by the People's Republic of China: In the city of Michin, in the center of the country, University of California scientist John Harte measured rain significantly higher in acidity than that which fell on Pitlochry.

The Dramatic Damage

The impact that acid rains have on aquatic ecosystems can be dramatic, especially those systems occurring in areas with granite, quartz, or similar rock. Such rocks, which have a low capacity to neutralize (or "buffer") the acidity, are widespread in the Appalachian and Rocky Mountains and throughout much of Canada, New England, and northern Europe. The lakes of southern Norway, for example, are in severe trouble. Populations of micro-organisms crucial to the lakes' economies have been altered, and fish populations have declined or disappeared.

The situation is especially critical in the Adirondacks. Not only are the rains acidifying the water there, but the sulfuric and nitric acids are causing chemical reactions in the soil that are releasing large quantities of aluminum. The acids accumulate in the snowpack in the winter. Then, when the snow melts in the spring, they pour into the lakes ... creating a flush of aluminum pollution. As a result, all fish have been killed in some 300 Adirondack lakes, and brook trout and other sensitive species may have been exterminated over the whole area. (Spotted salamanders, for example, cannot breed in acid snowmelt.)

In Canada, scientists have now identified 48,000 lakes that will become sterile in 20 years or so if the acid rains continue. And along with dams, overfishing, poaching, pesticides and other kinds of pollution, the rains threaten the economically valuable Atlantic salmon with extinction.

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