New Delhi:
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Up From Zero On Nov 1: Expert
Crop fires in Punjab and Haryana contributed as much as 70% of the pollution load in Delhi on Sunday , the city's worst air day in a long time, a leading government scientist said, basing his assessment on computer models used to determine the capital's air quality index.Gufran Beig, program di rector of Safar (System of Air Quality and Weather Forecasting and Research), under the earth sciences ministry, said on Monday that the proportion of pollutants from crop fires in Delhi's air rose dramatically from almost zero on November 1 to a peak of 70% on November 6.
“Safar's chemistry transport model gives a clear picture of the share of pollution from external sources. It shows pollution load from crop fires in Punjab and Haryana rose steadily after November 1 due to favourable upper air winds,“ Beig said.
The smog cleared significantly on Monday , helped by a pick-up in surface winds and a change in upper-air direction. “The share of cropburning in Delhi's air quality was down to 50% and dropping,“ the scientist said. Like a perfect storm, various factors fell in place to create the dense smog spell over NCR, which SAFAR programme director Gufran Beig described as an “extreme pollution event“.“While the surface air was calm over the capital, upper air wind direction changed around November 1, when winds blew in from between west and north, directly transporting pollutants from crop fires,“ the scientist said.
The calm surface winds and an air ridge over NCR prevented the pollutants from dispersing, leading to an accumulation of toxic chemicals in the air.
Beig said the PM 2.5 concentrations in Delhi's air were at unprecedented levels on Sunday .
“Since we started SAFAR five years ago, we have never seen the value of PM 2.5 concentrations crossing 700µg m3. Just as extreme weather events are increasing so are extreme pollution events such as this one,“ he said.
SAFAR's figures on contribution of biomass burning in Delhi's air pollution come on a day when Union environment minister Anil Madhav Dave said crop burn ing was responsible for just 20% of the pollution level in the national capital.
That figure is based on source apportionment studies that have variously put the external contribution to winter pollution in Delhi at 20% to 35%. Beig said these studies give an average which would hold true in general terms but can't be used for specific events.
“This is like telling you what the normal rainfall at a place is. SAFAR's figures, on the other hand, are based on the actual conditions that existed during this period,“ the expert said.
Due to surface winds picking up, Beig predicted that the pollution levels would drop on Tuesday , while still staying in “severe“ zone, and come down further to “very poor“ levels on Wednesday .
“Safar's chemistry transport model gives a clear picture of the share of pollution from external sources. It shows pollution load from crop fires in Punjab and Haryana rose steadily after November 1 due to favourable upper air winds,“ Beig said.
The smog cleared significantly on Monday , helped by a pick-up in surface winds and a change in upper-air direction. “The share of cropburning in Delhi's air quality was down to 50% and dropping,“ the scientist said. Like a perfect storm, various factors fell in place to create the dense smog spell over NCR, which SAFAR programme director Gufran Beig described as an “extreme pollution event“.“While the surface air was calm over the capital, upper air wind direction changed around November 1, when winds blew in from between west and north, directly transporting pollutants from crop fires,“ the scientist said.
The calm surface winds and an air ridge over NCR prevented the pollutants from dispersing, leading to an accumulation of toxic chemicals in the air.
Beig said the PM 2.5 concentrations in Delhi's air were at unprecedented levels on Sunday .
“Since we started SAFAR five years ago, we have never seen the value of PM 2.5 concentrations crossing 700µg m3. Just as extreme weather events are increasing so are extreme pollution events such as this one,“ he said.
SAFAR's figures on contribution of biomass burning in Delhi's air pollution come on a day when Union environment minister Anil Madhav Dave said crop burn ing was responsible for just 20% of the pollution level in the national capital.
That figure is based on source apportionment studies that have variously put the external contribution to winter pollution in Delhi at 20% to 35%. Beig said these studies give an average which would hold true in general terms but can't be used for specific events.
“This is like telling you what the normal rainfall at a place is. SAFAR's figures, on the other hand, are based on the actual conditions that existed during this period,“ the expert said.
Due to surface winds picking up, Beig predicted that the pollution levels would drop on Tuesday , while still staying in “severe“ zone, and come down further to “very poor“ levels on Wednesday .
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