Not every polluting gas is guilty of causing acid rain. Two are; two others aren’t.
🏛️ Must Know
Which Two Gases Actually Cause Acid Rain
- Nitrogen Oxide Is a Real Cause Excess nitrogen oxide in the air genuinely reacts with water and other chemicals. This forms nitric acid, a component of acid rain.
- Sulphur Dioxide Is a Real Cause Excess sulphur dioxide also reacts with atmospheric water to form sulphuric acid, another major component of acid rain.
- Carbon Monoxide Is Not Carbon monoxide is a toxic gas, but it is not a direct cause of acid rain.
- Ozone Is Not Either Ground-level ozone harms health and crops, but it is not a precursor to acid rain formation.
Good to Know
📘 Good to Know
How Acid Rain Actually Forms
- Emitted by Power Plants and Vehicles Sulphur dioxide and nitrogen oxides come mainly from coal-burning power plants and industry. Vehicle exhaust adds to this too.
- Chemical Transformation in the Air These gases react with water, oxygen, and other chemicals in the atmosphere to form sulphuric and nitric acids.
- Falls as Rain, Snow, or Fog These acids then fall to earth as acid rain, acid snow, or acid fog. This damages soil, water bodies, and buildings.
📝 Previous Year Questions
UPSC CSP 2022 — Which Gases Actually Cause Acid Rain
- UPSC 2022 Excess nitrogen oxide and sulphur dioxide cause acid rain. Carbon monoxide and ozone do not. See UPSC CSP 2022 GS Paper I, Q100. View this question.
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Great to Know
🌟 Great to Know
Why Acid Rain Still Matters for India
- Damages Monuments Acid rain has been linked to the discoloration and erosion of marble monuments. Concerns have been raised specifically about the Taj Mahal.
- Harms Soil and Water Bodies It can also acidify soil and freshwater bodies, affecting crop yields and aquatic life over time.
- Connects to Other PYQ Facts This same sulphur dioxide/nitrogen oxide pairing also underlies UPSC questions on WHO air quality guidelines and vehicular pollution norms.
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