73.

What is the cause of acid rain? How is it harmful to the environment?

Acid rain is caused by the presence of oxides of sulphur and nitrogen in the atmosphere. Oxides of sulphur are released into the environment mostly due to fossil fuel combustion, ore smelting and petroleum refining. Nitrogen oxides are released into the atmosphere largely due to automobile exhaust and fossil fuel combustion. SO₂ and NO₂ after oxidation and reduction with water form sulphuric acid and nitric acid respectively. These acids are major contributors to acid rain.




Harmful effects of acid rain. Acid rain:
(i) is toxic to vegetation and aquatic life. 
(ii) damages leaves of trees and plants and retards the growth of forests. 
(iii) damages buildings and statues,
(iv) corrode water conduct pipes resulting in the leaching of heavy metals such as iron, lead and copper into drinking water.