Q. 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?
a) 1, 2 and 3
b) 2 and 4 only
c) 4 only
d) 1, 3 and 4
Correct Answer: b) 2 and 4 only
Question from UPSC Prelims 2022 GS Paper
Explanation :
Acid Rain and Its Primary Causes
Acid rain is a term that refers to a mixture of wet and dry deposition from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. The primary causes of acid rain are emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx), which react with the water molecules in the atmosphere to produce acids.
Key Pollutants Involved in Acid Rain
Carbon monoxide (CO) is a colorless, odorless, and toxic gas, but it does not contribute to acid rain. It is primarily a concern because it can be harmful to human health, particularly in enclosed spaces.
Nitrogen oxides (NOx), including nitrogen dioxide (NO2) and nitric oxide (NO), are significant contributors to acid rain. They react with water, oxygen, and other chemicals in the atmosphere to form nitric acid, which can then fall to the ground in precipitation, contributing to the acidification of ecosystems.
Ozone (O3) is a molecule composed of three oxygen atoms. It is not a direct contributor to acid rain. Ozone at ground level is a harmful air pollutant and a key component of smog, but it does not form acidic compounds that lead to acid rain.
Sulfur dioxide (SO2) is a gas that is produced by volcanic eruptions and industrial processes, particularly the combustion of coal and oil at power plants and the smelting of mineral ores that contain sulfur. In the atmosphere, SO2 can oxidize to form sulfuric acid (H2SO4), which is a major component of acid rain.
Therefore, the correct answer is “2 and 4 only” because nitrogen oxides and sulfur dioxide are the pollutants that contribute to acid rain, while carbon monoxide and ozone do not.
