NEW DELHI: A new study by Nasa scientists has concluded that there is a strong link between agricultural fires in Punjab and Haryana and PM2.5 levels in Delhi during the post-monsoon months of October and November.
PM2.5 concentrations in Delhi, which is downwind to Punjab and Haryana, show a coherent increase — rising often from as low as 50 micrograms per cubic metres (µg/ m3) before the onset of the burning season to 300µg/m3 at the beginning of November when burning is under way.
During the crop burning season of 2016, the seven-day average peaked to a record high of 550µg/m3. This could also explain the severe smog episode in November 2016 when PM2.5 concentration peaked to more than 700µg/ m3 on November 5, 2016. But the study also cautions that the impact of emissions from local sources, including more than 9.5 million vehicles, industries and construction activities, cannot be ruled out. However, this study could give the government clues to averting smog episodes. While the link between crop burning and winter pollution peak was being speculated for long, this is the first scientific study to correlate fire counts in Punjab and Haryana with wind direction and parallel rise in PM2.5 concentrations in Delhi.
The study that analysed satellite data for 15 years (2002-2016) also revealed an increasing trend in crop fires. It found that there is a shift in the distribution of fires from October to November. This study, which has been accepted recently to be published in the journal of Aerosols and Air Quality Research (AAQR), uses fire data from satellites, pollution data from Nasa’s A-train sensors and PM2.5 concentrations measured at the US Embassy in Chanakyapuri.
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