The air quality in Delhi was recorded in the 'very poor' category on Wednesday. According to the Delhi Pollution Control Committee data, the Air Quality Index is at 313 in Anand Vihar, 305 in RK Puram, 325 in Mundka and 309 in Patparganj; all four in 'very poor' category. An AQI between 0and 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'. A senior scientist at the India Meteorological Department said favourable wind speed helped in the dispersion of pollutants on Tuesday evening.
However, the wind speed has reduced again which will allow pollutants to accumulate, he said.
According to the Ministry of Earth Sciences' air quality monitor, SAFAR, the share of stubble burning in Delhi's PM2.5 concentration rose to 23 per cent on Tuesday, the maximum this season so far.
It was 16 per cent on Monday, 19 per cent on Sunday and 9 per cent on Saturday.
The wind direction and wind speed were favourable for the transport of pollutants from farm fires in Punjab, Haryana and neighbouring regions on Tuesday.
The number of farm fires in neighbouring states was 1,943 on Monday – the highest so far this season, SAFAR said.
According to the India Meteorological Department, the predominant wind direction was westerly-northwesterly and the maximum wind speed was 4 kilometers per hour.
The minimum temperature was recorded at 13.8 degrees Celsius.
Calm winds and low temperatures trap pollutants close to the ground, while favourable wind speed helps in their dispersion.
The air quality index (AQI) is likely to improve slightly on Wednesday but pollution levels will rise again on Thursday, SAFAR said.
The central government's Air Quality Early Warning System for Delhi said the national capital's air quality was likely to remain “very poor” till October 31.
The air quality warning system said the ventilation index – a product of mixing depth and average wind speed – is likely to be around 4,000 metre square per second on Wednesday – unfavourable for dispersion of pollutants.
Mixing depth is the vertical height in which pollutants are suspended in the air. It reduces on cold days with calm wind speed.
A ventilation index lower than 6,000 sqm/second, with the average wind speed less than 10 kmph, is unfavourable for dispersal of pollutants.
Meanwhile, Delhi Chief Minister Arvind Kejriwal will launch 'Green Delhi' mobile application on Thursday, using which citizens can bring pollution-causing activities to the government's notice, Environment Minister Gopal Rai said on Tuesday.
There will be a deadline to address complaints and the chief minister will get a daily report about resolved and pending grievances.