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Delhi’s air quality remains ‘very poor’ for 3rd straight day
The 24-hour rolling average air quality index (AQI) was 333 at 10am, compared to 351 at 4pm on Tuesday, the season’s highest so far
Delhi’s pollution levels remained “very poor” for a third straight day on Wednesday, even as the 24-hour rolling average air quality index (AQI) was 333 at 10am, compared to 351 at 4pm on Tuesday, the season’s highest so far. On Diwali day, the AQI was 345, as the air quality deteriorated to the “very poor” zone for the first time .
The minimum temperature of 21.8°C on Wednesday was three degrees above normal. The mercury went up to 32.9°C a day earlier. Both the maximum and minimum were expected to stay in this range until the weekend.
Favourable meteorological conditions have allowed firecracker emissions to disperse. Delhi has recorded consistent easterly to south-easterly winds of up to 10 km per hour since Tuesday morning, blowing away pollutants accumulated after Diwali.
“From 6am on Tuesday, we had winds of 5-7 km per hour, which increased to 10 km per hour during the day. There was also ample dispersion as the daytime temperature was high and the sun was out, allowing both vertical and horizontal movement,” said an India Meteorological Department official.
The hourly PM 2.5 levels shot up to over 29 times the national permissible limit of 60 micrograms per cubic metre (µg/m³) in parts of Delhi on Diwali night (Monday). Delhi’s overall average PM 2.5 touched a peak of 675µg/m³ at midnight on Diwali day. It was the highest in four years since 2021, when the average touched 728µg/m³ on Diwali day that year.
The concentration was 91µg/m³ at 4pm on Monday and 223µg/m³ at 8 pm. There was a sharp dip in PM 2.5. It was 510µg/m³ at 6 am, but improved to 438µg/m³ at 8 am, 135µg/m³ by noon and 89µg/m³ by 3 pm, indicating the firecracker emissions dispersed by the next day.
A predominant easterly wind direction meant the overall stubble burning contribution to Delhi’s PM 2.5 levels was only 0.8% on Diwali day. It was 1% on Tuesday, according to the Centre’s Decision Support System. The contribution is expected to rise marginally to 2.6% on Wednesday and 4.4% on Thursday.
The Early Warning System forecasts showed the AQI is likely to remain in the “very poor” range until at least Friday. In the subsequent six days, it should oscillate between “poor” and “very poor” as northeasterly winds continue to keep stubble emissions away.
Indian Institute of Technology Delhi air pollution expert Mukesh Khare said stubble burning is almost negligible. “If the contribution was over 10%, the AQI would have shot up to close to severe, or possibly in that range. Favourable meteorological conditions have helped disperse pollutants swiftly, which was clearly from firecrackers.”
