Just months after people of Delhi-NCR enjoyed blue skies, the city’s air quality was at its worst this winter on Monday as calm winds blowing in an unfavourable direction trapped local pollutants and helped incursion of smoke from Punjab and Haryana, generated due to paddy stubble burning.
The wind speeds in the capital and neighbouring cities of the National Capital Region dropped to a lowest speed of 5kmph in the early hours of Monday, leading to accumulation of pollutants near the surface. To add to this, the Northwesterly wind direction made it easier for incursion of smoke generated by 3,453 farm fires reported in Punjab on Sunday. The combination of these two factors led to a spike on Particulate Matter 2.5 (PM 2.5) and Particulate Matter 10 (PM 10) pollution in the region.
Faster winds help dispersing pollutants that are suspended closer to the ground during cold conditions whereas calmer winds, dry and conditions help to trap pollutants closer to the surface.
PM 2.5 levels rose 10-13 times above the safe limit as prescribed by the Central Pollution Control Board. In Patparganj, a largely residential enclave of east Delhi, PM 2.5 levels were 711 micrograms/metre cube (ug/m3) around 10am, which were nearly 12 times above the prescribed PM 2.5 standard of 60 ug/m3. Not too far in Anand Vihar, PM 2.5 value in the morning hours between 8-10 am was 706 ug/m3. In central Delhi, the air quality monitoring station at Major Dhyanchand Stadium recorded PM 2.5 levels of 631 ug/m3 at 7am.
According to SAFAR (System of Air Quality and Weather Forecasting and Research) and India Meteorological Department (IMD), the air quality will continue to be in the ‘severe’ category till Wednesday. “The winds have been calm since Friday evening and in a Northwesterly direction. The day temperatures also dropped marginally on Sunday and Monday. The average wind speed has been 6-8 kmph. These calm winds have helped trap pollution emitted from different sources. On Sunday night, air quality in Delhi was worse than severe,” said Vijay Kumar Soni, senior scientist, IMD.
SAFAR also said that fire from paddy straw burning in Punjab and Haryana accounted for 38% of the PM 2.5 pollution in Delhi’s air. SAFAR agency said that the percentage share of smoke in Delhi’s air translated to a pollution load of about 140 ug/m3.
Data maintained by the Punjab Remote Sensing Centre showed that on Sunday, 3,453 fires were recorded using fine resolution satellite imagery. The total count of fires due to paddy straw burning now stands at 61,139, which is the highest since 2016. In 2016, Punjab had recorded 70,208 during the paddy harvest season.
The data also showed that of the 61,139 farm fires recorded in Punjab so far, 35,163 fires or 57% of them were recorded in just the last nine days. “We expect the harvest to end soon. The fires have declined gradually since Thursday and the end of the harvest is near,” said Krunesh Garg, Member Secretary, Punjab Pollution Control Board.
Data showed that there is no clear trend of decline as yet. The season’s highest fire count – 5036, was recorded on November 5 and since then, the state has recorded 3858, 4716 and 3453 fires on Friday, Saturday and Sunday, respectively. Updated fire count data from Monday was not available.
IMD scientists said that there might be some relief for residents of Delhi-NCR from Wednesday onward due to a change in wind direction. “We are likely to see easterly winds from Tuesday onward and under its influence, the air quality may improve from Wednesday. But this improvement might not be vastly significant,” Soni said.
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