According to the SAFAR Forecasting System, the contribution of crop residue burning in Delhi reached 41% of PM 2.5 levels on Saturday, the highest recorded this season.
According to the Central Pollution Control Board (CPCB) bulletin, the air quality index remained in the ‘severe’ category on Saturday and stood at 437 as against 462 recorded on Friday. The main pollutants were PM 2.5 and PM 10.
The percentage of stubble burning has been continuously climbing up to the level of PM 2.5 for the past few days, the incidents of stubble burning have increased and the wind direction has changed to North-West. The effective fire count on Saturday was 5,159, up from 3,299 on Friday. This number of fires of more than 5,000 is the highest ever figure as per the SAFAR system.
The share of stubble burning in the amount of PM 2.5 in Delhi was 8% on Wednesday, 25% on Thursday and 36% on Friday. Scientists associated with the Travel Forecasting System expect that emissions from stubble burning will increase further on Sunday.
Gufran Baig, Founder Project Director of SAFAR, said the increase in local wind speed has brought down the 24-hour average PM 2.5 level to 256 micrograms per cubic meter at 6 pm on Saturday. This figure is less than 435 micrograms per cubic meter at 6 pm on Friday. He said that PM 2.5 levels, however, remained in the ‘severe’ category and are not likely to fall further due to crop residue burning.
Delhi Pollution Control Committee (DPCC) officials said the wind speed picked up slightly between 11 am and 2 pm, leading to a slight drop in PM 10 and PM 2.5 levels. But calm returned in the evening, a senior official said. He said that some stations of DPCC were having wind speed of about 3 kmph or less in the evening, which is considered calm.
At Anand Vihar monitoring station, the PM 2.5 level was around 322 micrograms per cubic meter at 9 am on Saturday, and fell to 146 micrograms per cubic meter at 4 pm. At 6 pm, the level again rose to around 220 micrograms per cubic metre. DPCC data shows that the wind speed recorded at the station increased to 0.9 m/s at 2 pm, but dropped to 0.3 m/s at 6 pm.
The DPCC official said that PM 2.5 levels decrease in the afternoon as the warming of the environment can lead to vertical movement of pollutants, which start moving upwards.
At Mandir Marg monitoring station also, the wind speed increased to 0.9 m/s at 2 pm, but dropped to around 0.2 m/s at 6 pm. As a result, the PM 2.5 level fell to around 236 micrograms per cubic meter at 3 pm, but rose to 256 micrograms per cubic meter at 6 pm.
The Travel Forecasting System indicates that the air quality is likely to improve to the upper end of the ‘very poor’ category as winds continue to intensify. The India Meteorological Department had predicted strong winds on Saturday and Sunday. The Air Quality Early Warning System for Delhi indicates that the wind direction will remain north-westerly from Delhi on November 7 and 8, making it conducive to transportation of pollutants from crop residue burning.
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