Delhi’s air quality turned ‘severe’ again on Thursday due to unfavourable meteorological conditions like low wind speed that prevented dispersion of pollutants, authorities said.
The Central Pollution Control Board (CPCB) data showed the overall air quality index (AQI) in the ‘severe’ category, while the Centre-run System of Air Quality and Weather Forecasting (SAFAR) showed an AQI of 372, which falls in the ‘very poor’ category.
As per the CPCB data, 22 areas recorded severe pollution, while 13 witnessed ‘very poor’ air quality.
In NCR, Ghaziabad and Faridabad recorded severe air quality while Gurugram and Noida recorded ‘very poor’ air quality.
The overall PM2.5 level — fine particulate matter in the air with a diameter of less than 2.5 micrometer — was recorded at 322 and the PM10 level at 485 in Delhi, the CPCB said.
The national Capital recorded its second highest pollution level of the year on Sunday with an AQI of 450. The air quality remained ‘severe’ on Monday and Tuesday. There was slight drop in pollution level and the air quality moved to the ‘very poor’ category on Wednesday. On Thursday, the air quality again worsened and turned ‘severe’.
The Indian Institute of Tropical Meteorology (IITM) stated that the air quality is likely to improve marginally on Friday. The ventilation index is marginally favourable for dispersion of pollutants at 4,500 sqm/second, the IITM also said.
The ventilation index is the speed at which pollutants can disperse. A ventilation index lower than 6,000 sqm/second, with average wind speed less than 10 kmph, is unfavourable for dispersion of pollutants.
The overall air quality is likely to improve on Friday by a few notches, but will continue to remain in ‘very poor’ category during the next three days, stated the SAFAR. “Major reason for predicted increase is a decline in surface wind speed which will disperse pollutants slowly unlike yesterday [Wednesday]. Other meteorological factors are also not very favourable,” the SAFAR further said.
