The peak contribution of stubble burning in northwest India to air pollution in Delhi may not coincide with adverse meteorological conditions this year, Central Pollution Control Board member secretary Prashant Gargava said on Friday. This means that peak emissions from crop residue burning in Punjab and Haryana, which in the past have had more than 40% to 50% share in Delhi’s air pollution levels, may happen earlier than the usual time frame of around the second week of November, when weather conditions hinder dispersion of pollutants.
Speaking at a press briefing, Gargava said the reasons behind this include a slight shift in the harvest season, higher fire counts so far as compared to the previous year, and comparatively less area under cultivation of non-basmati variety of rice, or paddy, which leaves stubble in fields after harvest.
“With the efforts of agencies and governments, and the slightly early start to the burning, it looks like this time the peak contribution of stubble burning may not coincide with peak adverse meteorology in Delhi… We might see less contribution this year, but all of this depends upon meteorological factors at that time,” Gargava said.
Data presented by Gargava at the briefing showed land under cultivation of paddy has reduced as compared to last year. In Punjab, the area has fallen to 20.76 lakh hectares this year as compared to 22.91 lakh hectares last year. In Haryana, it has fallen to 4.27 lakh hectares this year as compared to 6.48 lakh hectares last year.
The Punjab government had advanced transplantation of paddy this year by 10 days, on June 10 as opposed to June 20, heeding concerns of farmers about labour shortages due to Covid-19. This resulted in early harvest, Punjab officials said. Similarly in Haryana, officials said paddy was sown about a week earlier than usual.
Contribution of stubble burning in Punjab and Haryana to particulate matter of 2.5 micrometres (PM2.5) in Delhi — fine particles suspended in the air — peaked at 56% on November 5, 2018, and last year to 44% on October 31, as per data from the Central government’s System of Air Quality and Weather Forecasting and Research (SAFAR).
Last year, between October 8 and November 15, stubble burning’s contribution to PM2.5 in Delhi was higher than 10% on 19 days and higher than 20% on six days, as per SAFAR data.
The peak contributions in the last two years have also been around the festival of Diwali, when there is burning of firecrackers and higher economic activity in the city and its markets. The peak also coincides with the time when temperatures are low and wind speed is calm in Delhi, characteristic of winter, which traps pollutants closer to the surface rather than dispersing them.
On Friday, as per SAFAR, the contribution of farm fires to PM2.5 in Delhi was estimated to be 18%, highest so far since count began October 10 onwards. The city’s average air quality index (AQI) improved to the ‘poor’ category, with a reading of 239, as compared to Thursday when it was 312, in the ‘very poor’ range.
As per a forecast from SAFAR, the improvement happened as wind speed picked up marginally, helping in dispersion of pollutants that had accumulated. On Saturday, the AQI is forecast to stay in the higher end of ‘poor’ category or lower end of ‘very poor’.
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