The Capital’s air quality turned “poor” on Sunday as the wind direction changed to northwesterly triggering a steep increase in pollution levels here.
Westerly and northwesterly winds bring dust from western regions as well as smoke due to the burning of crop residue in neighbouring States such as Punjab and Haryana, to Delhi and the NCR.
A day’s improvement
After fluctuating between the “poor” and “very poor” categories for over a week, the city’s air quality had improved to the “moderate” category on Saturday mainly due to a squall, which dispersed pollutants, and rainfall in neighbouring areas that subdued the effect of stubble burning.
On Sunday, however, pollution levels in Delhi shot up by around 100 points on the Air Quality Index (AQI), according to Central Pollution Control Board data. The CPCB stated that the AQI, which was 161 on Saturday, had risen to 258 by Sunday afternoon.
The higher the AQI of an area, the higher the pollution level. An AQI between 0 and 50 is considered “good”, 51 and 100 “satisfactory”, 101 and 200 “moderate”, 201 and 300 “poor”, 301 and 400 “very poor”, and 401 and 500 “severe”.
The Ministry of Earth Sciences’ and SAFAR, said, “The overall air quality of Delhi is back in the ‘poor’ category. The surface and boundary layer wind direction is northwesterly now.”
“An increase in stubble burning in the northern part of India has been observed. The circulation pattern is supportive for efficient biomass plume transport to Delhi,” SAFAR said.
It added that the share of smoke from stubble burning in Delhi’s PM2.5 concentration was 13% on Sunday, the highest in over a week. It was zero on Saturday and is likely to increase to 19% on Monday. “A considerable increase in biomass share in pollution contribution is expected over the next two-three days. AQI is forecast to deteriorate to ‘very poor’ category by Monday,” SAFAR said.
According to CPCB data, more than 3,000 stubble burning incidents have occurred in Punjab and Haryana since the harvesting of paddy crop started around September 25. During the corresponding period last year, the count was around 2,600.
The period between October 15 and November 15 is considered critical as a maximum number of stubble burning incidents takes place in this span in Punjab and adjoining States.
