This Diwali, Delhi’s air quality is likely to be relatively better than last year, when pollutant levels had reached perilous proportion, according to a government agency, Safar. The Safar forecast on Monday was based on prevailing meteorological conditions, which include low upper wind movement, a situation that prevents pollutant-laden air from stubble-burning regions from entering Delhi. The agency said the air quality index (AQI) would remain “very poor” if bursting of firecrackers was down by even 50 per cent compared to last year, but it would turn “severe” if the same volume of crackers were set off.
However, since moisture in Delhi’s air was increasing and morning temperature dipping, it might lead to an increase in the atmospheric holding capacity of the emissions coming from firecrackers, Safar said. “There is no likelihood of the repeat of 2016. Upper air winds that transport pollutants from distant sources such as the Indo-Gangetic Plains or the stubble-burning regions are quite low and unlikely to impact Delhi significantly,” it said.
The agency said anti-cyclone conditions were looming large, which is linked to the withdrawal of monsoon and it might slow down surface winds, resulting in slow dispersion and stagnation of local pollution. According to the forecast, the highest levels of PM10 and PM2.5, which are ultrafine particulates, are expected between 11pm to 3am on the intervening night of October 19-20 and air quality will start improving further from Oct 21.
Safar, which operates eight monitoring stations in Delhi, said the share of PM2.5 (relatively more harmful than coarser particles) in PM10 was expected to remain unchanged, unlike last year when it had increased by 10-20 per cent during the Diwali period, which had made the air more toxic.
“A ‘very poor’ AQI essentially means that people may suffer from respiratory illness on prolonged exposure to such air. On further dip in air quality, the AQI will turn “severe”, which may trouble even healthy people and seriously affect those with existing diseases,” the agency said.