Oct air second worst in 5 years, Pg4.

Key Highlights:

• Delhi's average Air Quality Index (AQI) in October was 223, the second-worst in five years, despite low farm fires and high rainfall.
• On Diwali, October 20, Delhi's AQI reached 345, surpassing the previous two years.
• Delhi experienced 'Poor' or worse air quality for nearly two-thirds of October, with the worst air recorded on October 30 at AQI 373.
• Farm fires' contribution to Delhi's PM2.5 load was minimal at 0.5% on October 30, with local sources dominating pollution.

Detailed Insights:

• Despite a Supreme Court relaxation on firecracker ban, this Diwali was the most polluted since 2021, indicating limited effectiveness of green crackers.
• NASA's Terra MODIS data showed a sharp increase in Aerosol Optical Depth (AOD) over Delhi in late October, correlating with increased haze due to weather conditions.
• Pollution hotspots like Jahangirpuri, Anand Vihar, and Bawana experienced sharp spikes in particulate matter (PM) levels at night due to calm winds.
• The Decision Support System (DSS) data indicated that transport sector (13.44%), Ghaziabad (13%), and Gautam Buddha Nagar (11.7%) were major contributors to Delhi's PM2.5 emissions.
• Unusually warm nights, high humidity, and light winds in October prevented pollutant dispersal, contributing to stagnant air and poor air quality.
• Data from the Indian Agricultural Research Institute showed that farm fires were at a five-year low, with 3,845 recorded between September 15 and October 31 across six states.

Key Concepts Involved:

• Air Quality Index (AQI): A measure of air quality based on concentrations of various pollutants.
• PM2.5: Fine inhalable particles with a diameter of 2.5 micrometers or less, posing health risks.
• Aerosol Optical Depth (AOD): A measure of the extinction of solar radiation by aerosols in the atmosphere.