Delhi’s air quality deteriorated back to the ‘very poor’ category, as the 24-hour average Air Quality Index (AQI) settled at 313, with secondary organic aerosols emerging as the biggest contributor to Delhi’s air pollution, accounting for 22.7 per cent of the pollution load, closely followed by domestic solid biofuel burning at 22.3 per cent.
According to source-apportionment estimates by the Indian Institute of Tropical Meteorology (IITM), vehicular emissions accounted for 19.3 per cent of the pollution, while secondary inorganic aerosols contributed 11.9 per cent.
The IITM predicted that the impact of stubble burning is anticipated to increase on Thursday, potentially worsening air quality further over the next few days.
According to the Air Quality Early Warning System (EWS) for Delhi, the particulate matter concentration in the air — PM2.5 and PM10 — is also set to see an increase for the next two days. Of the 58 monitoring stations that recorded data on Wednesday, only one station was in the ‘severe’ category, 34 were in the ‘very poor’ category, 22 in the ‘poor’ category and only one in the ‘moderate’ category. The air quality monitoring station in the Delhi Cantonment area recorded ‘moderate’ air quality, with an average AQI of 117.
Experts said sources of secondary organic aerosols include certain industries, diesel and petrol vehicles, and biomass burning.
The contribution of firecrackers, which had emerged as the biggest source on Monday and Tuesday following Diwali, dropped sharply to 7.4 per cent on Wednesday.
On Wednesday, mixed combustion accounted for 10.6 per cent of the pollution load, followed by waste burning, including municipal and plastic-rubber containing waste, at 2.1 per cent.
Wood burning contributed 1.2 per cent, while industrial emissions and mineral dust and ash accounted for 1 per cent and 0.9 per cent, respectively. Coal combustion contributed 0.7 per cent.
The India Meteorological Department (IMD) has forecast partly cloudy skies and mist or shallow fog in a few places during the morning hours on Thursday.