Air quality may worsen from today, stubble burning to add to Delhi’s woes
Delhi’s overall air quality index (AQI) improved a few notches on Tuesday from a day before on account of a higher wind speed, but remained in the “very poor” category, with scientists warning of a further deterioration from Wednesday as stubble fires in Punjab have peaked.
On Monday, 2,047 fires were observed over Punjab and crop residue burning may have already crossed the peak in Haryana and Uttar Pradesh, according to scientists. Farmers said the impact of stubble fires may wane by the time Diwali festivities begin.
The Central Pollution Control Board’s (CPCB) 4pm bulletin on Tuesday reported an overall AQI of 312. This was several points below the AQI of 353 recorded on Monday in Delhi.
Forecasts by various air monitoring agencies, however, said the respite would be short-lived and Delhi’s air quality may start deteriorating again from Wednesday as the high stubble burning count in Punjab and Haryana, and the continuation of northwesterly winds are likely to make things worse for Delhi.
Lower temperatures expected over the next few days will also trap pollutants closer to the surface, experts said.
On Tuesday, a maximum temperature of 32.4 degrees Celsius was recorded at the Safdarjung observatory, considered representative of Delhi’s weather. The minimum temperature settled at 14.4 degree Celsius, two degrees below normal.
The System of Air Quality and Weather Forecasting and Research, Indian Institute of Tropical Meteorology (IITM), showed that the impact of stubble fires was 23% on Monday but Delhi’s air quality improved because of favourable meteorological conditions.
“Favourable winds aided dispersion of pollutants in Delhi, otherwise air quality would have deteriorated. On October 24, there were 900 fires in Punjab; on October 25, there were 1,400 fires and on October 26, it had crossed 2,000. But we expect some deterioration in air quality on Wednesday as wind speed is likely to decline marginally,” warned Vijay Soni, scientist at India Meteorological Department (air quality management division).
“Every year, there are around 60,000 stubble fires cumulatively. This year, there have been over 16,000 fires in total until now. It appears like fires are peaking now,” Soni said.
Harinder Singh Lakhowal, general secretary, Bharatiya Kisan Union, Punjab, said fires may have peaked already or ar about to peak in a day or so. “Harvesting will be complete by November 10-15. This is the peak of stubble fires, pollution has increased in Punjab where fires are burning. This year fires are high because farmers are agitating together against the farm bills.”
“Wind speed increased to about 18 kmph on Tuesday at Safdarjung and so the impact of stubble fires was not felt as much. Wind speed will reduce from Wednesday and the direction will remain northwesterly, so the air quality is likely to deteriorate,” Kuldeep Shrivastava, head, regional weather forecasting centre, added.
The ventilation index was 12000 m2/s on October 27. It is likely to be 4000 m2/s on October 28 and 8000 m2/s on October 29. The ventilation index is a function of mixing height and the wind speed and defines the ability of atmosphere to disperse contaminants.
A ventilation index below 2,350 sq metres/second is considered poor. Mixing height is the height at which pollutants mix in the air.
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