The Danger of Acid Rain: Causes & Consequences-
Acid rain is one of several symptoms of industrial society’s current dependence upon hydrocarbons, or fossil fuels, as its primary source of energy. The fossil fuels include coal, oil and natural gas. Unlike global warming, which is a result of CO2 emissions, acid rain is caused by the release of various compounds which cause changes in the pH of soils and bodies of water.
pH is the scale measuring the difference between the alkalinity (base) and acidity of chemical compounds. It is measured on a scale between 0 and 14, where anything over 7 is more and more alkaline, anything under 7 is more and more acidic, and 7 itself is neutral. The scale is logarithmic, like the Richter scale, which measures seismic disturbances. This means that a reading of 5 is 10 times as acidic as a reading of 6, for example, while a reading of 4 is 100 times as acidic as 6.
There are two compounds which are of greatest concern in the formation of acid precipitation (snow can also be acidic). The first is sulfur dioxide (SO2), which is primarily associated with the burning of coal. Nitrogen Oxides (NOx: NO, NO2, NO3) are also problematic, however, and they are produced by the burning of fossil fuels generally, and indeed by all combustion (Dunn 1999).
Acid rain once became so bad in Europe that it was beginning to damage ancient monuments and buildings made of stone and brick, though the phasing out of coal in many areas is beginning to alleviate this problem.
The biggest concerns ecologically are that acid rain can change the acidity of rivers and lakes, as well as of soils. The first major event which brought the problem to public attention, for example, were major fish kills in Norway in polluted bodies of water. Different species of fish have different tolerances when it comes to the acidity of the water in which they live. Rainbow trout, for example, die at a pH of only about 6.65. Yellow perch, on the other hand, are more tolerant, but still die at a pH of 4.43 (Lansky 1993).
As mentioned, soils can also be damaged, which implies damage to vegetation, crops, and especially forests as well. The accumulation of acids in soils can lead to the leaching of two important plant nutrients-calcium and magnesium. Deficiencies of these naturally occurring nutrients in the soil can affect the heath of forests and other vegetation, leaving them stunted and unable to grow and renew themselves in a natural manner (Bright 1999).
In North America the effects of acid rain are most pronounced in the northeastern US, which remains heavily coal dependent in terms of its electricity production. In the southwestern Adirondack Mountains, for example, about 51% of the 450 lakes larger than 10 acres have a pH of 5.5 or less and 38% are so acidic that they can no longer support any fish at all (Lansky 1993:276). Forests are also stunted in many areas.
The problem is not confined within national borders either, since prevailing winds also carry acid precipitation produced in this area into southeastern Canada, which gets most of its electricity from hydro and nuclear facilities. A survey of 234 lakes in Nova Scotia, for example, found that one third have a pH under 5 and contain no fish, and 13 rivers in the province are too acidic to support salmon.
Acid rain provides one more on a long list of reasons for abandoning fossil fuels-and especially coal-in favor of cleaner, more sustainable alternatives.
References, additional readings:
Chris Bright (1999) “The Nemesis Effect,” World Watch, May/June.
Seth Dunn, (1999) “King Coal’s Weakening Grip On Power,” World Watch, September/October.
Mitch Lansky (1993) Beyond the Beauty Strip: Saving What’s Left of Our Forests,” Old Bridge Press.
