Consider the following : 1. Carbon monoxide 2. Methane 3. Ozone 4. Sulphur dioxide Which of the above are released into atmosphere due to the burning of crop/biomass residue?
- (a) 1 and 2 only
- (b) 2, 3 and 4 only
- (c) 1 and 4 only
- (d) 1, 2, 3 and 4 ✓ UPSC's answer
Why the answer is (d)
• Burning crop residue is incomplete combustion of biomass and releases a cocktail of pollutants.
• It emits carbon monoxide (1) and methane (2) directly, along with CO2, particulate matter and volatile organic compounds.
• Sulphur dioxide (4) is released from the sulphur in plant matter, and nitrogen oxides plus VOCs react in sunlight to form ground-level ozone (3).
• Stubble burning in Punjab–Haryana is thus a major contributor to Delhi's winter smog.
• Hence 1, 2, 3 and 4, option (d).
Why the other options are wrong
- (a) 1 and 2 only
- Ozone (secondary) and SO2 are also produced.
- (b) 2, 3 and 4 only
- Carbon monoxide is a major product of biomass burning.
- (c) 1 and 4 only
- Methane and ozone are also released/formed.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2019, held on 2 June 2019. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.