How Much Does Large-Scale Crop Residue Burning Affect the Air Quality in Delhi?

Area of Science:

• Atmospheric Chemistry and Air Quality

Background:

• Delhi experiences frequent severe air pollution events driven by elevated PM2.5 concentrations.
• The precise impact of crop residue burning on Delhi's air quality remains inadequately quantified, with limited effective control strategies.

Purpose of the Study:

• To quantify the contribution of post-monsoon crop residue burning in northwestern Indian states to Delhi's surface PM2.5 levels.
• To assess the effectiveness of current fire emission control approaches.

Main Methods:

• Utilized the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem).
• Employed the FINNv1.5 fire emission inventory for sensitivity experiments.
• Validated model results with ground-based observations from Delhi, Punjab, and Haryana.

Main Results:

• Nonlocal fire emissions contributed an average of ~20% to Delhi's PM2.5 during the post-monsoon season.
• During severe pollution events, fire emissions accounted for 50-75% (80-120 μg/m3) of PM2.5 in Delhi.
• Highlighted the combined influence of external transport and local emissions on PM2.5 pollution.

Conclusions:

• Crop residue burning is a major driver of severe air pollution in Delhi.
• Effective air quality management requires addressing both regional fire emissions and local pollution sources.