Acid rain is a term for rain, snow, sleet, or other wet precipitation that is polluted by such acids as sulphuric acid and nitric acid. Acid rain harms thousand lakes, rivers, and streams worldwide, killing fish and other wildlife. It also damages buildings, bridges, and statues. High concentration of acid rain can harm forests and soil.
Acid rain forms when vaporised water in the air reacts with certain chemical compounds. These compounds, including sulphur dioxide and nitrogen oxides, come largely from the burning of coal, gasoline, and oil. Most vehicles, factories, and power plants burn such fuels for energy.
Regions affected by acid rain include large parts of eastern North America, Scandinavia and central Europe and parts of Asia. Since about the 1950s, the problem has increased in rural areas. This has occurred because the use of taller smokestacks in urban areas has enabled the winds to transport pollutants farther from their sources.
Adding lime to lakes and rivers and their drainage areas temporarily neutralizes their acidity. But the neutralization may have harmful side effects.