Acid rain is a matter of great global concern and has become one of the major environmental problems. The term ‘acid rain’ used first by Robert Angus Smith, the Chief Alkali Inspector of UK in 1872, described the acidic
nature of rain falling around Manchester. Acid rain is commonly defined as “a condition in which acidic after reacting chemically with pollutants the air”.
Among air pollutants sulphur and nitrogen are significant compounds. In particular, sulphur dioxide (S02) and oxides of nitrogen (NO and N02) are released from a variety of sources sulphur dioxide reacts in air to form sulphur trioxide. In turn sulphur trioxde reacts rapidly with atmospheric moisture to produce sulfuric acid.
Sulphur trioxide + Water sulfuric acid.
Similarly, the oxides of nitrogen react in air to produce nitric acid. Both these acids are very strong acids. These materials, when present in the atmosphere, dissolve in water droplets and fall to earth as acid rain.
Under normal conditions, rain water is slightly acidic because carbon dioxide dissolves in it and reacts to form a weak acid, which is not harmful. But main’s contribution through fossil fuel , power plants, industries, automobiles has disturbed this natural acidic balance and inverted natural rain into precipitated acid rain with several environmental implications.
The ill effects of acid rain can be found on vegetation, soil, marine resources, monuments as well as on man. Air pollutants and acids generated by industrial activities are now entering forests at an unprecedented scale. Many forests in Europe and North America now receive as much as 30 times more acidity than they would if rain and snow fell without pollutants. Its reaction includes change in colour of leaves, premature drops of leaves and flowers, tree crowns progressively thin, and ultimately, trees die. Marine resources can be totally devastated with loss of aquatic life, fishes can die and entire lakes and streams can be destroyed. The affected fishes, if consumed by humans and birds, cause dangerous effects. In soil, the rate of decomposition of organic matter and formation of nitrogen fixing organisms is reduced by acids. Human health may also be affected increasing respiratory and skin problems.
Acid rain is an increasing problem in industrial areas of America, Europe and Asia. Where large amount of fossil fuels are burned. The ill effects of acid rains have no national limits as nature knows no geographical boundaries. Only developed technology can save the world from ill effects
of acid rain.