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Bad air days begin, AQI slips to ‘poor’

Delhi’s overall AQI on Saturday was 284, CPCB data showed, compared with 198 on Friday, which just about remained in ‘moderate’ category
Air quality continued to worsen in the national capital as the evening progressed, with 18 out of 36 areas showing readings of “very poor” that could lead to respiratory illness.(ANI Photo)
Updated on Oct 17, 2021 12:27 AM IST
BySoumya Pillai, Hindustan Times, New Delhi

People in Delhi will have to wait for the east wind and some likely showers on Sunday to find relief from deteriorating air quality that fell to the “poor” category on Saturday, even as the burning of farm residue in Punjab, Haryana and Pakistan continued to rise.

Delhi’s overall air quality index on Saturday was 284, Central Pollution Control board data showed, compared with 198 on Friday, which just about remained in the “moderate” category. The federal pollution watchdog considers a reading of 201-300 as “poor” that leads to breathing discomfort to most people on prolonged exposure. A reading of 101-200 is considered “moderate”.

Air quality continued to worsen in the national capital as the evening progressed, with 18 out of 36 areas showing readings of “very poor” that could lead to respiratory illness.

There could be easterly winds and light to moderate rainfall to wash away the pollutants, the India Meteorological Department predicted on Saturday.

Satellite images from NASA’s fire tracker showed a spike in the number of “red dots” that indicate stubble burning on October 16 from three days ago.

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Delhi chief minister Arvind Kejriwal, who has been posting the city’s air quality recordings over nearly a month to establish how stubble burning in Punjab and Haryana impacts Delhi’s air, tweeted NASA data Saturday.

The drop in Saturday’s air quality was due to the increase in farm fires in the neighbouring agrarian states of Punjab, Haryana and parts of Pakistan, weather forecasters said. It was made worse by calm winds, leading to an accumulation of pollutants in the atmosphere.

“Till Saturday afternoon, Delhi was receiving winds from the north-west direction, which was carrying with it smoke from the stubble fires in Punjab and Haryana. However, the wind direction will now change to easterly,” said Mahesh Palawat, vice-president, meteorology and climate change at private forecaster Skymet Weather Services. “When the wind direction is transitioning, thespeeds reduce drastically and this leads to an accumulation of pollutants already present in the air.”

The wind will start blowing from the east from Sunday morning, according to VK Soni, head of Met department’s environment and research centre.

The respite might be short as pollution levels are likely to rise again from October 19, Soni said.

The primary pollutant on Saturday in Delhi was PM 2.5, according to the System of Air Quality and Weather Forecasting and Research (Safar) run by the ministry of earth science. PM 2.5, or dust particles less than 2.5 micrometres wide, that results primarily from combustion, gets deposited deep into the lungs and even enter the bloodstream, causing severe damage to health. Till last week, the primary pollutant in Delhi’s air was PM 10, or particulate matter with diameter less than 10 micrometres that is mostly dust from local sources.

“With 1572 fire counts as per SAFAR harmonised methodology, which includes data of two ISRO (Indian Space Research Organisation) satellites, the stubble burning contribution in Delhi’s air has suddenly increased to 14%,” SAFAR’s analysis said. “Fire counts are gradually increasing and north-westerly winds at a speed of 900 mb is favourable for transporting stubble smoke into Delhi.” The share of farm fires was 6% on Friday.

Experts have warned of the impending air emergency, an annual occurrence in Delhi in autumn, as soon as the winds change back to north-westerly.

The stubble burning this season started slow because the southwest monsoon withdrew later than usual from parts of northwest India and because of some policy decisions by the government, said Pawan Gupta, a research scientist at the Goddard Earth Sciences Technology and Research, Universities Space Research Association.

“The stubble fires were merely delayed,” Gupta said.

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