COURTESY HT JAN 16

Delhi air in toxic zone, could get worse today

Soumya Pillai

letters@hindustantimes.com

New Delhi : Already in the “severe” category, Delhi’s air quality deteriorated further on Friday with the AQI nearly maxing out at several monitoring stations and the India Meteorological Department (IMD) warning that the pollution levels may rise further and enter the “severe plus” or “emergency” category by Saturday.

The Central Pollution Control Board (CPCB) recordings showed the overall air quality index (AQI) in the Capital at 460, deteriorating from Thursday’s 429.

The temperatures in Delhi rose slightly on Friday but IMD scientists said the respite was brief, adding mercury will fall again from Saturday before it starts to rise again on January 18.

On Friday, the minimum temperature at the Safdarjung observatory, considered representative of Delhi’s weather, settled at 6.4 degree Celsius, a notch below the season’s normal. The maximum temperature was 20.8 degree Celsius. On Thursday, the minimum temperature was recorded at 2 degree Celsius, five degrees less than what is considered normal for the season.

IMD scientists said the minimum temperature would hover around 4-5 degree Celsius on Saturday and Sunday, and would slightly rise from Monday.

CPCB’s hourly recordings of particulate matter levels also showed a rising trend. At 6pm on Friday, the PM 2.5 levels (ultrafine particulate matter with diameter less than 2.5 micrometres) had remained above the 300ug/m3 mark for over 22 hours. The PM 10 (particulate matter with diameter less than 10 micrometres) was also inching closer to the 500ug/m3 mark.

The acceptable standards of PM 2.5 levels in India is 60ug/m3 and for PM 10 is 100ug/m3.

IMD scientists said the pollution levels are expected to get worse through Friday night and the air quality is likely to reach “emergency” levels by Saturday.

VK Soni, head of IMD’s environment monitoring and research centre, said that an improvement is likely only from January 18, when the wind direction will change from north-westerly to easterly.

“The winds are calm and the ventilation conditions are not favourable for the dispersion of pollutants. There is a forecast for pollution levels deteriorating even more through Friday night. The levels will stay in the ‘severe plus’ zone even on Saturday,” said Soni.

At 7pm on Friday, a number of air quality monitoring stations were nearly maxed out. The hourly average AQI in RK Puram, Mathura Road, Jawaharlal Nehru Stadium, Patparganj, Ashok Vihar, Rohini, Narela, Okhla phase-II and Chandni Chowk had reached above 480. The maximum value on the AQI scale is 500.

Union ministry of earth science’s air quality monitoring centre, System of Air Quality and Weather Forecasting and Research (Safar), said the city-state was looking at the “first prolonged extreme air pollution event of 2021”. “Extremely low ventilation and shallow boundary layer height is adding to the severity. Surface winds are calm and the minimum temperature is likely to fall further from Saturday. The AQI is forecasted to deteriorate further and rapidly,” the Safar forecast read.

Boundary layer is the lowest part of the atmosphere, which changes according to factors such as temperature. The lower the boundary layer, lesser the space for pollutants to mix with air and disperse. This leads to pollutants being trapped closer to the ground.

Despite the warning from the IMD and Safar, the Commission for Air Quality Management (CAQM) and the Central Pollution Control Board (CPCB) are yet to issue any precautionary directions under the Graded Response Action Plan (Grap).

The last order issued by the CAQM had extended the ban on hotmix plants and stone crushers in Delhi till January 2.

CAQM head MM Kutty did not respond to HT’s calls or messages to seek a response