The air quality in Delhi has sharply deteriorated as winter approaches, with particulate matter (PM 2.5) levels consistently exceeding 300, categorising the air quality as ‘very poor’. This decline is closely linked to the seasonal practice of stubble burning in neighbouring states, particularly Punjab and Haryana, where farmers burn leftover paddy stalks to prepare fields for the winter wheat crop. This age-old agricultural practice has implications for urban air quality, particularly in the National Capital Region.
About Stubble Burning
Stubble burning is a traditional method used by farmers to quickly clear fields post-harvest. The practice has gained notoriety due to its environmental repercussions, contributing to air pollution. Farmers often resort to this method due to the limited time available between the rice and wheat harvests, compounded by rising labour costs which make alternative clearing methods less viable. Despite its efficiency, stubble burning releases a plethora of pollutants, exacerbating the already poor air quality, especially in urban areas.
Impact on Air Quality
Research indicates that stubble burning contributes between 20% to 40% of the PM 2.5 levels in Delhi during the winter months. Advanced modelling techniques have allowed researchers to quantify the impact of stubble fires on air quality, demonstrating that even a slight increase in burning correlates with spikes in pollution levels. For instance, a recent study brought into light that every additional fire incident could elevate PM 2.5 levels by approximately 12.44 units.
Seasonal Variations and Pollution Sources
The transition from monsoon to winter affects wind patterns, leading to a build-up of air pollutants close to the ground. This phenomenon is exacerbated by stubble burning, particularly when winds blow from Punjab and Haryana towards Delhi. Interestingly, while stubble burning peaks in October and November, the majority of Delhi’s pollution persists even in winter months when this practice ceases. This indicates that other sources, such as vehicular emissions and industrial activities, also play important role in the city’s air quality crisis.
Contributions from Other Sources
Recent analyses reveal that while stubble burning accounts for a notable percentage of Delhi’s pollution, transport-related emissions are equally , contributing around 18% of PM 2.5 levels. Furthermore, secondary inorganic aerosols (SIA), which form from the reaction of gaseous pollutants, contribute to the overall pollution load. Studies show that SIA can account for up to 32% of winter pollution, with a majority stemming from sources beyond Delhi.
Policy Responses and Future Directions
Recognising the multifaceted nature of air pollution, policymakers have begun to advocate for an airshed approach, which involves coordinated efforts across states to tackle pollution collectively. This strategy acknowledges that air quality management cannot be confined to Delhi alone, as pollution sources often originate from surrounding regions. Collaborative initiatives are essential for implementing effective solutions to mitigate the air quality crisis.
Questions for UPSC:
- Discuss the impact of stubble burning on air quality in Delhi and its implications for public health.
- Analyse the role of secondary inorganic aerosols in contributing to air pollution in urban areas.
- Evaluate the effectiveness of current policy measures aimed at reducing air pollution in Delhi.
- What are the alternative methods to stubble burning that can be adopted by farmers to manage crop residue?
- Examine the significance of an airshed approach in addressing transboundary pollution issues.
