The emissions, which cause acid rain, come chiefly from power stations and road traffic. Acid rain damages buildings as well as plant and animal life. It comes from sulphur containing in coal and oil. When fussil fuel is burnt, sulphur dioxide (SO₂) is formed. Then it is oxidized by reaction with oxygen to produce SO₃ gas, which combines with water in the air to produce droplets of sulphuric acid (H₂SO₄), a major component of acid rain. Nitrogen monoxide from exhaust fumes and industrial emissioms is also oxidized in the air and mixes with water to form nitric acid. Sulphic and nitric acids are carried long distances with air currents and fall as acid rain. Acid rain can travel thousands of miles, so pollution in one country can become acid rain fir another country.

The effects of acid rain vary enormously according to the type of soil on which it falls. Alkaline soils based on limestone can neutralize large amounts of acid, whereas peat or granite soils have very little ability to do so. The ability of certain chemicals within the rock (such as calcium carbonate) to reduce the acidity of the water is called natural buffering. But if the lake lies on an insoluble of acid rock such as granite, no natural buffering will occur and the acidity of the water will remain high. The problem first came to light in Scandinavia because its geology makes it especially sensitive to the effect of acid rain. In those places where the soil does not contain enough alkalis, which are needed to neutralize the acid, the fish in many lakes and rivers are poisoned by high acid concentrations. Scientists have tried to reduce the acidity of lakes artificially by adding chemicals to the water, but this intended remedy sometimes upsets the ecological balance even further

Part 3

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