(Eds: Rpt after adding words in para 4)New Delhi, Oct 29 (PTI) The level of emissions fromfireworks fell by around 40 per cent during Diwali festivitiesthis time as compared to 2016, according to the findings of astudy which assume importance in the light of a region-wideban on the sale of firecrackers by the Supreme Court.
The SAFAR study concluded that, as a whole, the Diwaliperiod (October 18-22) was the cleanest since 2014. Level ofparticulates did shoot up a day after Diwali, but thedispersion was quicker and air quality attained the pre-Diwalilevel within three days.
SAFAR, a central government air quality monitoringagency, based its findings on a detailed study of air quality,sources of emissions and meteorological conditions whichprevailed in the national capital during this period.
As compared to emissions from fireworks in 2016, the dipwas significant: 50 per cent on October 19, the Diwali night;25 per cent on October 20, when pollution peaked and 45 percent on October 21, SAFAR (System of Air Quality and WeatherForecasting And Research) said in its report released today.
But if less firecrackers were burnt, what explains thefact that air quality turned "severe" for the first time in2017, a day after Diwali?The amount of PM2.5, an ultrafine particulate measuringless than 20 times the width of a human hair, recorded bySAFAR during the period went like this: October 18 - 136,October 19 - 174, October 20 - 407, October 21 - 203 andOctober 22 - 139 micrograms per cubic metre (ug/m3). The 24-hour safe standard is 60 (ug/m3).
SAFAR project director Gufran Beig explained thatreduction in emissions from a particular source and reductionin levels of pollution are not linearly related or directlyproportional.
He said that "incredible" amount of fireworks, despitethe relative reduction, on Diwali night led to trapping ofsmoke in the air and a rapid build-up of pollutants,especially between midnight and 4 am on October 20, aided by afall in temperature and lowering of mixing height (where airand suspended particulates mix).
"Emissions slow down local wind movement as air becomesheavy. It's like the heaviness in air one feels in a room whenthe number of occupants go up, say from five to 20. Butsubsequently, the air cleaned up faster this time due towarmer temperature and dry conditions.
"The ban on crackers certainly had an impact. The daysthat preceded and followed Diwali saw restraint from people.
Usually, crackers are set off before and after the actualnight of festivities as well. The real impact could be seen onOctober 20," Beig told PTI.
He said the post-Diwali air had also been good ascompared to last year as the smoke from stubble burningregions in Punjab and Haryana had not reached Delhi because ofthe wind direction, which was not the case last year resultingin the worst smog episode that the city witnessed in nearlytwo decades.
External contributions, such as stubble burning, did notexceed 10 per cent of the total pollution load during thisperiod, the SAFAR report said.
The study factored in the observed meteorological dataincluding wind speed, wind direction, satellite estimate ofstubble burning emissions among other factors, it said. PTISBR SMNSMN.
This is unedited, unformatted feed from the Press Trust of India wire.
