What is Acid Rain?

Acid rain means rainfall with a pH of less than 5.6. About 80% of the oxides of sulphur come from the burning of fossil fuels. Sulphur trioxide on reaction with water produces sulphuric acid (H₂SO₄), which is the principal (60-70 percent) cause of acid rain. Acid rain is essentially an outcome of aggressive industrialisation in developed countries and is caused by both natural processes (like lightning, volcanic activities, forest fires) and human activities (combustion of fossil fuels in automobiles, factories and power plants).