Farm fires accounted for 14% of the PM2.5 pollution in Delhi on Tuesday. (File)
The share of stubble burning in Delhi PM2.5 pollution rose to 32 per cent on Wednesday, the highest this year so far, amid raging farm fires in Punjab and favourable conditions for transport of emissions to Delhi-NCR.
The Indian Agricultural Research Institute (IARI) reported 3,634 farm fires in Punjab on Wednesday, the highest this year so far.
The number stood at 1,842 on Tuesday, 2,131 on Monday, 1,761 on Sunday, 1,898 on Saturday and 2,067 on Friday. SAFAR, a forecasting agency under the Union Ministry of Earth Sciences, said the share of stubble burning in Delhi's PM2.5 pollution increased to 32 per cent due to favourable transport-level wind speed.
Transport-level winds blow in the lowest two layers of the atmosphere-the troposphere and stratosphere -- and carry smoke from farm fires to the national capital region.
Moderately favourable surface-level wind speed (up to 8 kmph), however, did not allow rapid accumulation of pollutants, meteorology experts said.
Farm fires accounted for 14 per cent of the PM2.5 pollution in the national capital on Tuesday, 22 per cent on Monday, 26 per cent on Sunday and 21 per cent on Saturday, according to the System of Air Quality and Weather Forecasting and Research (SAFAR).
PM2.5 are fine particles that are 2.5 microns or less in diameter and can travel deep into the respiratory tract, reaching the lungs and entering the bloodstream.
The Commission for Air Quality Management had last week said the increased incidents of stubble burning in Punjab this year "is a matter of serious concern". Along with unfavourable meteorological conditions, paddy straw burning in adjoining states is a major reason behind the alarming spike in air pollution levels in the national capital in October and November.
Farmers set their fields on fire to quickly clear off the crop residue before cultivating wheat and vegetables.
According to the IARI, Punjab reported 71,304 farm fires between September 15 and November 30 last year and 83,002 farm fires in the corresponding period in 2020.
Last year, the share of farm fires in Delhi's PM 2.5 pollution peaked to 48 per cent on November 7. According to an analysis by the Delhi Pollution Control Committee, people in the national capital breathe the worst air between November 1 and November 15 -- the period when stubble burning peaks.
The city records an average PM2.5 concentration of 285 micrograms per cubic metre from November 1 to November 15. PM 2.5 level from 61 to 120 is considered "moderate to poor", 121 to 250 is "very poor", 251 to 350 is "severe" and more than 350 is "severe plus".
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