Dip in Wind Speed Likely to Turn Delhi-NCR's Air Quality 'Severe' Again by Thursday

New Delhi: The national capital recorded its best air quality in 12 days as moderate winds continued to counter the effect of stubble burning on Monday, officials said.

However, weather experts said, pollution levels are likely to enter the 'severe' zone again on Thursday due to a gradual dip in wind speed over the next two-three days.

The overall air quality index in Delhi stood at 214 at 4pm, a notch below Sunday's AQI of 215. Jahangirpuri was the most polluted area with an AQI of 311 and Ayanagar (98) the least polluted, according to the Central Pollution Control Board data.

Neighbouring Ghaziabad (256), Greater Noida (218), Noida (227) recorded their air quality in the 'poor' category, while Gurgaon's AQI (138) remained in the 'moderate' category for the second consecutive day.

Kuldeep Srivastava, a senior scientist at the India Meteorological Department, said the maximum wind speed dropped from 30 kilometers per hour on Sunday to 18 kilometers per hour on Monday.

"The wind speed is likely to reduce to 10-12 kmph on Tuesday and to 5-6 kmph on Wednesday," he said. The Ministry of Earth Sciences' air quality monitor SAFAR said the AQI is predicted to deteriorate to the lower end of the 'very poor' category by Tuesday.

The probability of the AQI touching the lower end of the 'severe' category on November 21 is high, it said.

"Another factor is the change in transport-level wind direction to northwest (coming from Punjab and Haryana) and an increase in the effective fire count to 610.

"As transport-level winds are predicted to slow down to moderate level, favouring (farm fire plume) intrusion in Delhi, the share of stubble burning is estimated to increase to 13 percent in Delhi's PM2.5 pollution on Tuesday," it said.

Meanwhile, the Supreme Court-mandated anti-pollution authority, EPCA, on Monday asked Delhi and NCR states to step up surveillance and enforcement to check local sources of pollution and crop burning in view of the predicted dip in air quality.

In a letter to the chief secretaries of Delhi, Uttar Pradesh, Punjab and Haryana, Environment Pollution (Prevention and Control) Authority Chairman Bhure Lal said hot mix plants, ready mix plants, and stone crushers will continue to remain closed in Delhi-NCR.

The Supreme Court had on November 4 banned construction and demolition activities in the region till further notice.

Due to slow wind speed and very little ventilation, dispersion of pollutants will not happen and there is a likelihood that the air quality will slip back to the 'very poor' category and even the 'severe' category, the EPCA chief said.

The situation will worsen if there's light rain, which would be inadequate to wash away the pollutants and add to the moisture instead, he said.