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Air quality worsens, enters severe category

PUBLISHED ON DEC 29, 2019 11:50 PM IST

New Delhi: A cloud layer that has enveloped the city, increased humidity levels and slow winds together pushed Delhi’s air quality further into the ‘severe’ zone on Sunday, with the Air Quality Index (AQI) spiking to 431, according to the Central Pollution Control Board (CPCB).

Sunday’s AQI was a drop of more than 20 points from Saturday, when the index was recorded as 409, which is also considered to be in the ‘severe’ category. The CPCB’s 4pm bulletin recorded Friday’s AQI as 373, in the ‘very poor’ category.

There has also been an increase in particulate matter (PM) levels in the city’s air over the last two days. Data shows that PM 2.5 (particulate matter with diameter less than 2.5 micrometres) levels increased from 243ug/m3 at 11pm on Saturday to 273ug/m3 at 8pm on Sunday, inching closer to the emergency mark of 300ug/m3.

The same trend was observed in PM10 (particulate matter with diameter less than 10 micrometres) levels. From 383ug/m3 at 11pm on Saturday, PM10 levels spiked to reach 423ug/m3 at 8pm on Sunday. The emergency mark for PM10 levels in the air is 500ug/m3.

Scientists at the India Meteorological Department (IMD) said a thick cloud layer over northern India is the primary reason behind the lack of circulation. This, coupled with an increase in relative humidity and low wind speed, has resulted in pollution particles getting trapped closer to the surface.

“The wind speed on Sunday remained below 10kmph, and weather conditions in general are also making dispersion of pollutants difficult,” said Kuldeep Srivastava, head of IMD’s regional weather forecasting centre.

Another senior IMD scientist said the AQI is likely to remain in the ‘severe’ zone on Monday. From Tuesday morning, however, wind speeds are expected to pick up, bringing some respite for Delhi residents.

“There is also a forecast of rain from January 1 to January 3. This will also help bring down pollution levels in Delhi,” the IMD scientist said.

A System of Air Quality and Weather Forecasting and Research (Safar) forecast said Vinobapuri, Okhla and Noida are likely to emerge as pollution hotspots in the next 48 hours.

“By December 31, through improving surface winds speed and ventilation, air quality will begin to improve. A significant improvement in AQI, along with visibility condition is expected by New Year’s day,” the Safar forecast read.

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