Every year in October, Delhi's air quality starts to dip, and a war of words between different government erupts . On October 15, it was clear that stubble burning is not only caused by air pollution in Delhi dust, vehicular pollution, and wind also plays an important role in air pollution .
October usually marks the withdrawal of monsoons in northwest India. During monsoons, the prevalent direction of the wind is easterly. These winds, which travel from the Bay of Bengal, carry moisture and bring rains to this part of the country. The winds change direction to northwesterly once the monsoon withdraws .during summers, too, the direction of the wind is northwesterly and storms carrying dust from Rajasthan and sometimes Pakistan and Afghanistan. According to a national physical laboratory, 72% of Delhi's wind in winters comes from the northwest, .while the remaining 28% comes from the Indo – Gangetic plains.
A dip in temperatures is also behind the increased pollution levels. As temperature dips, the inversions of height, which is the layer beyond which pollutants cannot disperse into the atmosphere's upper layer, are lowered. Also, high-speed winds are very effective at dispersing pollutants, but winters bring a dip in wind speed overall compared to summers.
WHAT IS THE ROLE OF FARM FIRES ?
The government of Punjab and Haryana was to conserve groundwater, passed the law delay of sowing of paddy. There is less time for farmers to harvest paddy, clear the sowing field for the next cycle. The paddy straw and stalks have high silica content and are not used to feed live stocks. The easiest way to clear the field is to set it on fire.
In 2015, Delhi's air pollution conducted by IIT Kanpur stated that 17.26% of all particulate matter in Delhi in winters is because of biomass burning.
WHAT ARE THE OTHER BIG SOURCES OF POLLUTION IN DELHI?
Dust and vehicular pollutions are the two biggest causes of dipping air quality in Delhi in winters. Dry cold weather means dust pollution contributes to 56% of PM 10 and PM 2.5 load at 59 t/d, the top contributors being road 38 % of PM 2.5 concentration, the IIT Kanpur study said.
Vehicular pollution is the second biggest cause of pollution in winters. According to the IIT Kanpur study,20% of PM 2.5 in winters comes from vehicular pollution. The government introduces BS-VI (cleaner ) fuel to reduce vehicular pollution .
During the lockdown this year, Delhi saw among the cleanest air since 2015. It also saw above-average temperature in September, which meant the air remained cleaner for longer.
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