Low wind speed allowed pollutants to accumulate in the air
A layer of eye-stinging smog lingered over Delhi on Monday as its air quality neared the 'severe' zone with stubble burning accounting for 22 per cent of the city's PM2.5 pollution.
Delhi's 24-hour average air quality index (AQI) stood at 392 (very poor), worsening from 352 on Sunday. It was 354 on Thursday, 271 on Wednesday, 302 on Tuesday and 312 on Monday (Diwali).
An AQI between zero 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".
Low wind speed allowed pollutants to accumulate in the air and the situation might deteriorate to "severe" on Tuesday morning, said Mahesh Palawat, vice president (meteorology and climate change), Skymet Weather.
He said humidity may increase and the wind speed may reduce further from November 4 under the influence of a strong Western Disturbance leading to another episode of smog. According to SAFAR, a forecasting agency under the Union Ministry of Earth Sciences, the share of farm fires in Delhi PM2.5 pollution stood at 22 per cent on Monday. It was 26 per cent on Sunday, the highest this year so far, and 21 per cent on Saturday.
Palwat said the transport-level wind direction and speed is favourable for transport of smoke from stubble burning. According to an analysis by the Delhi Pollution Control Committee, people in the capital breathe the worst air between November 1 and November 15 -- the period when stubble burning peaks.
The city records an average PM2.5 concentration of 285 micrograms per cubic metre from November 1 to November 15. PM 2.5 level from 61 to 120 is considered "moderate to poor", 121 to 250 is "very poor", 251 to 350 is "severe" and more than 350 is "severe plus".
The Indian Agricultural Research Institute (IARI) reported 2,131 farm fires in Punjab on Monday - the highest so far this season, 1,761 on Sunday, 1,898 on Saturday, 2,067 on Friday and 1,111 on Thursday. It logged 70 and 20 cases of stubble burning in Haryana and Uttar Pradesh, respectively, on Monday.
The CAQM had on Thursday said the increased incidents of stubble burning in Punjab this year "is a matter of serious concern".
Environment Minister Gopal Rai said Punjab would have seen a large reduction in stubble burning had the Centre supported the state government's "mega plan" to provide cash incentive to farmers for not burning crop residue.
With pollution levels worsening, the Centre's air quality panel had on Saturday directed authorities to impose a ban on construction and demolition activities in Delhi-NCR, except in essential projects, and other curbs under stage three of the Graded Response Action plan GRAP.
GRAP is set of anti-air pollution measures followed in the capital and its vicinity according to the severity of the situation.
The next stage in the "Severe Plus" category or Stage IV can include steps like a ban on the entry of trucks into Delhi, allowing 50 per cent of staff to work from home in public, municipal and private offices,closure of educational institutions and the plying of vehicles on an odd-even basis, etc.
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