UPSC Prelims 2022 Question:

Consider the following

1. Carbon monoxide
2. Nitrogen oxide
3. Ozone
4. Sulphur dioxide
   
   

Excess of which of the above in the environment is/are cause(s) of acid rain?

Explanation: 

• Acid rain refers to the ways in which acid from the atmosphere is deposited on the earth’s surface. Oxides of nitrogen and sulphur which are acidic in nature can be blown by wind along with solid particles in the atmosphere and finally settle down either on the ground as dry deposition or in water, fog and snow as wet deposition.
  
  
• Burning of fossil fuels (which contain sulphur and nitrogenous matter) such as coal and oil in power stations and furnaces or petrol and diesel in motor engines produce sulphur dioxide and nitrogen oxides. SO2 and NO2 after oxidation and reaction with water are major contributors to acid rain, because polluted air usually contains particulate matter that catalyse the oxidation.
  
  

Therefore, option (2) is the correct answer.

Subject: Environment|Pollution