Why is Delhi’s air quality deteriorating?

(Source – The Hindu, International Edition – Page No. – 10)

 Declining Air Quality in Delhi

• The withdrawal of the southwest monsoon and the onset of winter have led to deteriorating air quality in Delhi, with PM 2.5 levels exceeding 300, indicating ‘very poor’ conditions.
• This drop in air quality aligns with the seasonal practice of stubble burning in Punjab, contributing significantly to pollution levels.

Stubble Burning: A Traditional Practice

• Stubble burning involves incinerating leftover paddy stalks after harvest, commonly used by farmers in Punjab and Haryana due to limited time to prepare fields for winter wheat.
• Rising labour costs make alternatives like mechanical shredding expensive, leading to continued reliance on burning, despite environmental concerns.

Contribution to Air Pollution

• Studies indicate a strong correlation between wind direction from Punjab and Haryana and pollution spikes in Delhi; each additional fire incident increases PM 2.5 levels by about 12.44 units.
• Research suggests that stubble burning contributes approximately 20% to 40% of Delhi’s air pollution, peaking at 35% during critical periods.

Seasonal Trends and Pollution Dynamics

• The transition from monsoon to winter reduces wind speed, causing pollutants to settle closer to the ground; thus, additional sources like stubble burning can significantly impact the AQI.
• Over 50% of Delhi’s pollution is attributed to external sources, indicating that local spikes can dramatically raise the AQI.

Beyond Stubble Burning: Other Pollution Sources

• Despite a reduction in stubble burning incidents—from 17,467 in 2018 to 1,749 in 2023—Delhi’s air quality remains poor, suggesting other significant contributors.
• Transportation emissions account for around 18% of PM 2.5 levels, while secondary inorganic aerosols (SIA) from outside Delhi contribute significantly to overall pollution.

A Need for Coordinated Action

• The ongoing poor air quality, even after stubble burning has stopped, highlights the need to address other pollution sources effectively.
• The Indian Institute of Tropical Meteorology advocates for an airshed approach, necessitating collaborative efforts across multiple states to tackle the air quality crisis and improve conditions in Delhi and its vicinity.