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Pollution likely to rise in coming days in NCR, warns EPCA; writes to states to check farm fires

Nov 18, 2019 09:37 PM IST

New Delhi: Though Delhi breathed easier on Monday, it stares at another smog episode in the coming days due to slowing winds, a likely increase in fog cover and

New Delhi: Though Delhi breathed easier on Monday, it stares at another smog episode in the coming days due to slowing winds, a likely increase in fog cover and a drop in mercury, allowing little ventilation, the Supreme Court-appointed Environment Pollution (Prevention and Control) Authority (EPCA) warned on Monday.

The apex court-panel wrote to the governments of Haryana, Punjab and Uttar Pradesh to “step up surveillance” and curb local sources of emissions, including those from crop residue burning.

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Delhi’s air quality could plunge to ‘very poor’ or even ‘severe’ between Tuesday and Thursday on account of a combination of factors, the authority said.

“The Centre-run system for pollution forecasting and research informed that wind direction during this period is favourable for intrusion of stubble burning. If burning is not checked, its contribution to overall pollution in Delhi could increase up to 13%,” said Bhure Lal, chairperson, EPCA, in his letter to chief secretaries of the three states.

The air quality index (AQI), as calculated by the Central Pollution Control Board’s (CPCB) 4pm bulletin on Monday, was 214 in the ‘poor’ category. On Sunday, the AQI was 215 when air quality had improved to ‘poor’ after a four-day spell of pollution levels remaining in the ‘very poor’ and ‘severe’ categories.

“The air in the region finally improved after days of dense and hazardous smog. However, the India Meteorological Department (IMD) alerted that from Tuesday (November 19) to Thursday (November 21), there will be little wind and ventilation, which will not allow pollutants to disperse. Hence, the air quality could slip back to ‘very poor’ or ‘severe’ levels again,” the letter read.

This situation could be further aggravated if there is scant rain, as it will not be adequate to wash away the pollutants but will instead add more moisture to the air, facilitating accumulation of pollutants, Lal said.

“We have seen this phenomenon in the past few weeks that when increased moisture allowed trapping of pollutants and created a cloud of haze and smoke, it resulted in a sharp drop in air quality,” he added.

On November 3, Delhi saw its worst day in terms of air quality since 2016 when the AQI had spiralled to 494. The situation was caused by secondary pollutants (more harmful than levels of ultrafine particulate matter 2.5), which had formed because of high moisture resulting from scant rainfall the previous day.

According to IMD scientists, air quality could deteriorate on November 20-21 due to a host of factors – low wind speed, cloud cover, moderate fog and drop in mercury, which together result in a toxic combination of smog.

The average wind speed on Monday was 18-20 kilometre per hour (kmph), which is favourable for dispersion. This is expected to reduce to 10-12 kmph on Tuesday and further to 4-6 kmph on Wednesday.

“High moisture content due to a fog cover traps pollutants while cloud cover bars sunlight from reaching the surface. Visibility in the morning hours may reduce to 300 metres. With a drop in temperature, the air becomes cold and heavy. Also, from Wednesday, the wind direction will also have an easterly component, which too brings moisture. All these factors can lead to accumulation of pollutants, which would not be dispersed if wind speed is low,” said Kuldeep Srivastava, head, regional weather forecasting centre, IMD.

In addition to this, the mercury will drop by two to three degrees Celsius on Wednesday, when the minimum temperature is expected to be around 12 degrees Celsius while the maximum temperature may settle at 24 degrees Celsius.

On Monday, the night temperature was recorded as 15.3 degrees Celsius, three notches above the season’s average, while the day temperature was 26.5 degrees Celsius, a notch below normal.

According to the bulletin released by the System of Air Quality and Weather Forecasting and Research (Safar), a unit of the union Ministry of Earth Sciences (MoES), the share of stubble burning to overall pollution in Delhi was 9% on Monday and it could rise up to 13% on Tuesday. It was much higher than 2% on Sunday.

“Accumulation of pollutants leading to a sharp deterioration in air quality is predicted by November 20-21 when air quality may reach ‘severe’ category,” the forecast by Safar said.

ends

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