ACID PRECIPITATION
The Four Corners power plant in New Mexico. This facility burns coal, sending
the smoke up high into the atmosphere with these stacks, each over 65 meters
tall. The smoke that the stacks belch out contains high concentrations of
sulfur, which smells bad (like rotten eggs) and produces acid when it combines
with the water vapor in air. The intent of those who designed the plant was
to release the sulfur-rich smoke high up in the atmosphere, where the
winds would disperse and dilute it. This sort of solution to the problem posed
by burning high-sulfur coal was first introduced in Britain in the mid-1950s,
and rapidly became popular in the United States alone. Basically they function
to carry the acid produced by the fuels away from the areas where they are
produced: London no longer suffers from acid fogs, but the forests and lakes
of Sweden are being destroyed.
The environmental effects of this acidity are serious. The sulfur introduced
into the upper atmosphere combines with water vapor to produce sulfuric acid,
and when the water later falls as rain or snow, the precipitation is acid.
Natural rainwater rarely has a pH lower than 5.6; in the northeastern United
States, rain and snow now have a pH of about 3.8, about a hundred times as
acid as the usual limit. Because the prevailing winds in the temperate
latitudes (where most industries are concentrated) are westerlies, the sulfur
emissions released by plants in the midwestern United States primarily return
to the earth in rain and snow that falls in the eastern United States and
Canada, and similar patterns occur in Europe.
Acid precipitation destroys life. Thousands of the lakes of
northern Sweden and Norway no longer support fish; these lakes are now eerily
clear. In the northeastern United States and eastern Canada, tens of thousands
of lakes are dying biologically as a result of acid precipitation. At pH levels
below 5.0, many fish species and other aquatic animals die, unable to reproduce
under these conditions. In southern Sweden and elsewhere, groundwater
is now regularly found to have a pH between 4.0 and 6.0, its acidity resulting
from the acid precipitation that is slowly filtering down into the underground
reservoirs, thus threatening the water supplies of future generations.
Trees also suffer. There has been enormous forest damage in the Black Forest
in Germany and in the forests of the eastern United States and Canada. It
has been estimated that at least 3.5 million hectares of forest in the
northern hemisphere are being affected by acid precipitation and the problem
is clearly growing.
Its solution at first seems obvious: capture and remove the emissions instead
of releasing them into the atmosphere. There are, however, serious difficulties
in executing this solution. First, it is expensive. Reliable estimates
of the cost of installing and maintaining the necessary "scrubbers"
in the United States are on the order of 4 to 5 billion dollars per year.
Although this is not more than one percent of the amount that will ultimately
be spent to "bail out" failed savings and loan associations, our
national priorities evidently do not clearly focus yet on a healthy environment.
An additional difficulty is that that the polluter and the recipient of the
pollution are far from one another, and neither wants to pay so much for what
they view as someone else's problem. The Clean Air Act revisions of 1990 addressed
this problem in the United States significantly for the first time.
