Burning of firecrackers on Diwali coupled with pollutants from farm fires in neighbouring states led to the air quality deteriorating in the capital, though pollution levels remained lower than the last three years. Data from the Central Pollution Control Board (CPCB) shows the average air quality index (AQI) of the city on Monday was 368 — in the ‘very poor’ category — less than 390 recorded a day after Diwali last year. In 2017, the figure was 403, in the ‘severe’ category, and in 2016 it was 445.
However, the central government’s System of Air Quality and Weather Forecasting And Research (SAFAR) said the city’s air quality was ‘severe’ on Monday, with 506 AQI overall as of 7 pm.
According to SAFAR, the average 24-hour concentration of particulate matter of 2.5 micrometres (PM2.5) was above the CPCB’s prescribed ‘severe’ standard of 250 micrograms per cubic meter air. According to SAFAR, this was noted across its nine monitoring stations as well as many stations of the Delhi Pollution Control Committee (DPCC).
The DPCC, on the other hand, said there was a reduction in pollution and a drop of around 30% in concentration of PM2.5, sulphur dioxide and carbon monoxide. “The reduction in air pollution indicators has been recorded even though, as per the latest satellite imagery, fires on farm lands in Punjab and Haryana are at peak and even more in number in comparison to the same period last year,” DPCC said, adding that less concentration of pollutants show that fewer firecrackers were burned this year.
A DPCC official said action is being taken to control local sources of air pollution and that they have been largely brought under control. This includes stopping use of diesel generator sets, mechanised sweeping of roads, and shifting industries to piped natural gas. “The factors deteriorating the air quality are external,” the official said.
On Monday, the city skies were overcast with smog. A scientist from the India Meteorological Department (IMD) said the sky one kilometre above the ground was clear and that there were no clouds over Delhi. “What you could see was concentration of pollutants from stubble burning, bursting of firecrackers and other local sources. This is likely to stay this way over the next two to three days,” the scientist said.
Unfavourable west-northwesterly wind direction is bringing external pollutants to Delhi and light wind speed of around 7-8 km/hour being recorded at present is not enough to disperse pollutants that are accumulated in the air, the IMD scientist said.
Data from the CPCB shows there have been over 12,000 farm fire instances in Punjab and more than 3,700 in Haryana between September 23 and October 27. “We are seeking a report from the two states on the high number of farm fires recorded this year,” a CPCB official said. According to SAFAR, PM2.5 contribution from farm fires was 15% on Monday.
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