After a brief respite, the air quality level across several areas in Delhi-NCR deteriorated to ‘severe’ category on Tuesday. According to data available on government air quality monitoring service SAFAR, the AQI at SiriFort, Lodhi Road, ITO were 401, 456 and 436 respectively. The average AQI on Monday was 360.
A combination of factors such as a change in wind direction, lower temperatures and local wind speed are likely the reasons behind Delhi’s plummeting air quality levels.
“AQI is likely to deteriorate to ‘severe’ category for the next two days. Improvement towards ‘very poor’ is predicted only by November 14,” SAFAR said. The share of stubble burning in Punjab and Haryana in Delhi’s air is expected to increase to 25% Tuesday from 18% Monday.
As per the data available on Central Pollution Control Board, PM 2.5 is the major pollutant in Lodhi Road and the average AQI is 392 which is in the “very poor” category. In ITO, the AQI was recorded in the “severe” category with PM 2.5 as the major pollutant.
Cooler temperatures Tuesday and Wednesday may reduce the atmospheric boundary layer height and lead to accumulation of pollutants closer to the surface. According to experts, factors leading to this build-up are varied, with the impact of meteorology, higher share of combustion pollutants, and external biomass and dust contribution among the primary reasons.
SAFAR officials said local surface wind speed needs to rise to help flush out pollutants. SAFAR officials added, “Impact of stubble burning in Delhi has varied because some days there might be high fire counts but the wind direction might not be towards the city.”
Meanwhile, the ongoing odd-even policy in the capital has been relaxed for two days in wake of 550th birth anniversary celebrations of Guru Nanak.
An AQI between 0-50 is considered ”good”, 51-100 ”satisfactory”, 101-200 ”moderate”, 201-300 ”poor”, 301-400 ”very poor” and 401-500 ”severe”. Above 500 falls in the ”severe plus” category.