Why in the News?
A recent study by the Centre for Research on Energy and Clean Air (CREA) highlights that secondary pollutants, particularly ammonium sulphate, are responsible for nearly one-third of India’s PM2.5 pollution.
What are Primary Air Pollutants?
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About Secondary Air Pollutants:
- Definition: Secondary pollutants form in the atmosphere through chemical reactions involving primary pollutants and environmental agents like sunlight and water vapour.
- Formation Factors: Their creation depends on weather, sunlight, and existing pollutants, making them more complex.
- Key Examples:
- Ammonium sulphate and nitrate – from SO₂ and NH₃ reacting in the air.
- Ground-level ozone (O₃) – formed when NOₓ and VOCs react under sunlight.
- Acid rain components – such as sulfuric and nitric acids.
- Photochemical smog – a mix of toxic secondary pollutants in urban air.
- Impact: They contribute heavily to PM2.5 pollution and have long-lasting, widespread effects.
Highlights from CREA’s Study:
- Ammonium Sulphate Share: This secondary pollutant accounts for 34% of India’s PM2.5, averaging 11.9 μg/m³ nationwide.
- Source Link: It forms from SO₂ (mainly from coal plants) reacting with ammonia from fertilisers and waste.
- FGD Compliance: Only 8% of India’s coal plants have installed flue gas desulphurisation (FGD) units, despite regulations.
- High Exposure Zones: Within 10 km of coal plants, ammonium sulphate levels are 2.5 times higher than in distant areas.
- NCAP City Impact: In 130 cities, it contributes 20–43% of PM2.5; in 114 cities, the share exceeds 30%.
- Other Contributors: Ammonium nitrate and similar secondary compounds form up to 50% of PM2.5 in many places.
- Policy Suggestions: The study urges rapid FGD rollout, fertiliser reform, and strict pollution control enforcement.
| [UPSC 2013] Photochemical smog is a resultant of the reaction among-
Options: (a) NO 2 , O 3 and peroxyacetyl nitrate in the presence of sunlight * (b) CO 2 , O 2 , and peroxyacetyl nitrate in the presence of sunlight (c) CO, CO 2 , and NO 2 at low temperature (d) high concentration of NO 2 , O 3 and CO in the evening |
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