Description

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Context:

A recent study by the Centre for Research on Energy and Clean Air (CREA) reveals that secondary pollutants, especially ammonium sulphate, account for nearly 34% of PM2.5 pollution in India.

About Air Pollution:

Air pollution—particularly fine particulate matter (PM₂.₅)—has become a major environmental and public health challenge in India. Traditionally, policy and public attention have focused on primary pollutants (e.g., dust, vehicle exhaust, industrial emissions).

However, recent research by the Centre for Research on Energy and Clean Air (CREA) highlights the growing impact of secondary pollutants, formed through atmospheric reactions and constituting up to one-third of India’s PM₂.₅, necessitating fresh policy attention.

What Are Secondary Pollutants?

Primary pollutants are directly emitted (e.g., SO₂ and NOₓ from coal plants/vehicles, ammonia from fertilizers and livestock).
Secondary pollutants arise in the atmosphere when primary emissions undergo chemical transformations (e.g., reaction of SO₂ with NH₃ to form ammonium sulfate ((NH₄)₂SO₄), or NOₓ with VOCs to yield ozone and nitrates).
They are harder to trace and control due to meteorological dependencies and long-range transport across regions.

Key Findings from CREA Study

Aspect	Details
Contribution of Ammonium Sulfate to PM₂.₅ (Nationwide)	~34%
Average Nationwide Ammonium Sulfate Concentration	11.9 µg/m³
Main Source of SO₂ (Precursor to Ammonium Sulfate)	Coal-fired power plants (>60% of national SO₂ emissions)
Ammonium Sulfate Levels Near Power Plants	15 µg/m³ within 10 km
Ammonium Sulfate Levels Beyond 10 km	6 µg/m³
Concentration Range in NCAP Cities (130 Cities)	20–43% of PM₂.₅
Cities with Contribution >30% (Out of 130)	114 cities
Contribution of Other Secondary Pollutants	Ammonium nitrate, organic aerosols.
Total Contribution of Secondary PM₂.₅ (Combined)	Nearly 50% of the total PM₂.₅

Why It Matters?

Health hazards: PM₂.₅ penetrates deep into lungs, causing respiratory, cardiovascular illnesses, and increased mortality.
Environmental effects: Secondary aerosols exacerbate acid rain, reduce visibility, and impair ecosystems.
Transboundary impact: Secondary pollutants travel across states and regions, affecting air quality far from source areas

Policy Gaps & Regulatory Challenges

Inadequate control of precursor emissions: Though FGD (Flue Gas Desulphurization) is mandated, only ~8% of Indian coal plants have installed them. Some reports suggest rolling back the mandate, posing a serious risk.
Neglected ammonia emissions: Agriculture is a major NH₃ source, but fertilizer use reforms remain inadequate.
NCAP focuses on primary PM: The current NCAP (targeting a 20–30% reduction in PM by 2025–26) lacks emphasis on secondary pollutants and cross-sectoral coordination.
Inter‑state coordination failure: Pollution transport between regions undermines local efforts without a broader air‑shed management framework.

Way Forward:

Measure	Action Points
Strict enforcement of FGD rules	- Mandate Flue Gas Desulfurization (FGD) in thermal power plants - Impose heavy penalties for non-compliance
Regulate ammonia sources	- Promote balanced fertilizer use- Encourage nitrification inhibitors - Manage livestock waste effectively to curb NH₃ emissions
Expand the NCAP mandate	- Include targets for secondary pollutants such as ammonium sulfate and nitrate - Improve real-time monitoring of precursor gases using dense sensor networks
Inter-sectoral airshed governance	- Establish regional governance bodies - Ensure participation from state governments, agriculture, industry, and power sectors for joint air quality planning
Enhanced research and modelling	- Invest in high-resolution atmospheric models - Use satellite-based tools like MERRA‑2 to monitor and predict secondary pollutant patterns

ALSO READ- https://www.iasgyan.in/daily-current-affairs/only-32-indian-cities-had-clean-air

Source: The Hindu

PRACTICE QUESTION

Q. Discuss the emerging challenge of secondary pollutants like ammonium sulphate in India’s PM₂.₅ pollution and suggest policy measures to address it. (150 words)