Air quality in Delhi drops to seasonal low despite 50% cut in stubble burning

It may improve after November 6 from an anticipated rise in windspeeds

A day before Deepavali, air quality has dipped to a seasonal low of 320 — or the “very poor” category in the Delhi National Capital Region. Despite a spike in instances of farm fires from Punjab and Haryana this week, they aren’t a contributor to the quality, according to meteorological analysts.

There were close to 2,700 instances of stubble burning on Wednesday and on Tuesday, 3000 instances recorded from Punjab, 203 from Haryana and 87 from Uttar Pradesh. “The contribution of biomass burning in PM2.5 concentration is likely to be less than 5% as winds are not favourable for transportation of pollutants,” according to an analysis from the Air Quality Early Warning System of the Ministry of Earth Sciences.

The air quality over Delhi is likely to remain poor, at least until November 6 and then improve from an anticipated rise in windspeeds. Moisture and the lack of adequate winds also lower the mixing height that then retards the natural dispersion of pollutants. A mixing height less than 6,000 m with average wind speed less than 10 kmph is unfavourable for dispersion of pollutants. Currently the mixing depths are around 1,700 m and windspeeds less than 10 kmph.