Delhi’s air quality remained in the ‘very poor’ category on Wednesday, with the city recording an AQI of 313 at 4pm, even as firecracker emissions continued to affect pollution levels after Diwali and the contribution from stubble burning was forecast to rise to 20.3% on Thursday.
Data from the Indian Institute of Tropical Meteorology’s real-time source-apportionment system showed that firecrackers contributed 7.4% of Delhi’s emissions between 1am and 9am on Wednesday. Their share had been substantially higher earlier in the week, reaching more than 80% during the same period on Monday after widespread firecracker use following Diwali.
Firecrackers accounted for 43.4% of Delhi’s pollution contribution on Sunday, according to the IITM data. Their share rose to more than 80% between 1am and 9am on Monday, while the full-day contribution stood at 71.1%. On Tuesday, firecrackers still contributed 22% of the pollution load.
The Central Pollution Control Board’s 24-hour average bulletin placed Delhi’s AQI at 313 on Wednesday afternoon. The reading had briefly improved to 299 on Tuesday, at the higher end of the ‘poor’ category, after wind speeds increased. Delhi Technological University was the only monitoring station to record ‘severe’ air quality on Wednesday, with an AQI of 414.
The pollution mix shifted as the impact of firecracker emissions began to decline. Between 1am and 9am on Wednesday, secondary organic aerosols were the largest identified source at 22.7%, followed by domestic solid biofuel or dung-cake burning at 22.3% and vehicles at 19.3%. Secondary inorganic aerosols contributed 11.9%, mixed combustion 10.6% and firecrackers 7.4%.
Secondary organic aerosols are formed when volatile organic compounds released by vehicles, industries, solvents and vegetation react with other substances in the atmosphere, producing particulate matter. Secondary inorganic aerosols develop when gases including sulphur dioxide, nitrogen oxides and ammonia undergo chemical reactions that create particles such as sulphates and nitrates.
Northwesterly winds were expected to remain consistent, conditions under which the contribution from crop-residue burning was forecast to increase to 20.3% on Thursday. Delhi’s air quality was expected to remain in the ‘very poor’ category over the following two days.
The latest readings also highlight how Delhi’s pollution burden changes across sources rather than being driven by a single cause. Firecracker emissions dominated immediately after Diwali, but transport, solid-fuel burning and secondary chemical formation remained significant contributors as the week progressed.
The Supreme Court had permitted only green crackers during two time windows—6am to 7am and 8pm to 10pm—on November 7 and 8. The report said the restriction was widely flouted, with firecrackers being used until early Sunday morning. Earlier coverage had also reported that Delhi markets were selling conventional firecrackers carrying fake green labels.
