Consider the following : Carbon monoxide Nitrogen oxide Ozone Sul

Consider the following :

  • Carbon monoxide
  • Nitrogen oxide
  • Ozone
  • Sulphur dioxide

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

1, 2 and 3
2 and 4 only
4 only
1, 3 and 4
This question was previously asked in
UPSC IAS – 2022
The correct answer is B) 2 and 4 only.
Acid rain is primarily caused by atmospheric pollutants, specifically sulfur dioxide (SO₂) and nitrogen oxides (NOx). These gases react with water, oxygen, and other chemicals in the atmosphere to form sulfuric acid and nitric acid.
Statement 1 (Carbon monoxide) is incorrect. Carbon monoxide (CO) is a pollutant but does not cause acid rain.
Statement 2 (Nitrogen oxide) is correct. Nitrogen oxides (NOx, including NO and NO₂) are major precursors to nitric acid formation in acid rain.
Statement 3 (Ozone) is incorrect. Ozone (O₃) is a secondary pollutant and a greenhouse gas. While it can contribute to the oxidation processes that form acid rain from SO₂ and NOx, it is not a precursor acid gas itself and is not considered a primary cause in the same way as SO₂ and NOx.
Statement 4 (Sulphur dioxide) is correct. Sulphur dioxide (SO₂) is a major precursor to sulfuric acid formation in acid rain.
The main sources of SO₂ and NOx emissions are the burning of fossil fuels (coal, oil, natural gas) in power plants, industries, and vehicles. Acid rain can harm forests, lakes, streams, and damage buildings and monuments.