Stubble burning share in city's pollution rises to 36%; air quality becomes 'severe'

New Delhi: Delhi's air quality on Thursday entered the "severe" category for the first time since January after a sharp spike in farm fires was reported in Punjab, Haryana, Uttar Pradesh and other neighbouring states. The Central government's air quality monitoring agency said the share of stubble burning in Delhi's PM2.5 pollution rose to 36 per cent on Thursday — also the highest this season so far.

NASA's satellite imagery showed a large, dense cluster of fires that covered most parts of Punjab and some regions of Haryana. The number of farm fires in neighbouring states was 2,912 on Wednesday, the highest so far this season, according to the Ministry of Earth Sciences' air quality monitor SAFAR.

"Stubble burning share in Delhi PM2.5 concentration was 36 per cent on Thursday," it said. It was 18 per cent on Wednesday, 23 per cent on Tuesday, 16 per cent on Monday, 19 per cent on Sunday and nine per cent on Saturday.

The Centre's Air Quality Early Warning System for Delhi said a significant increase in the number of fire points was observed over Punjab (around 3,000), Haryana and Uttar Pradesh on Wednesday which is likely to impact the air quality of Delhi-NCR and other parts of northwest India.

Experts have attributed the spike in pollution to calm winds and low temperatures, which have allowed the accumulation of pollutants amid a spike in farm fires. "Extremely calm surface and boundary layer winds along with the low nighttime boundary layer height resulted in low ventilation...practically stagnant, no dispersion condition has resulted in the current situation," SAFAR said.

Delhi recorded an air quality index (AQI) of 402 at 2 pm. The 24-hour average AQI was 297 on Wednesday, 312 on Tuesday, 353 on Monday, 349 on Sunday, 345 on Saturday and 366 on Friday. An AQI between 0 and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.

SAFAR said the accumulation of locally generated pollutants and increased external intrusion due to north-northwesterly boundary level winds from regions where stubble is burnt were major factors for the increase in PM 2.5 levels.

An increase in surface wind speed and better ventilation conditions are likely to "significantly" improve the situation by Saturday, it said. According to the India Meteorological Department, the predominant wind direction on Thursday was northerly and the maximum wind speed was 8 kilometers per hour. Calm winds and low temperatures trap pollutants close to the ground, while favourable wind speed helps in their dispersion.

Ahead of Diwali, when pollution levels usually see drastic spikes, the Delhi government has already announced the launch of an anti-firecracker campaign. Environment Minister Gopal Rai on Wednesday said the campaign will begin from November 3 and residents will be encouraged to participate in a "no crackers" campaign. He added that the government will do its best to promote the sale of green crackers and will strictly enforce Supreme Court guidelines on the sale and manufacture of polluting crackers.