Why there is sudden rise in pollution in Delhi ?

Everybody is aware about the 'Kadwi Hawa' of Delhi but only few know the reason behind the pathetic condition of its atmosphere. It is being said that stubble burning, vehicle exhaust and too much of construction activities in Delhi are biggest contributor of pollution. 

However that is not the complete story, because vehicle exhaust and construction are daily business in the city and stubble burning is carried out in other times of the year. It is the combination of different types of factors which has led Delhi towards this annual crisis. Not only Delhi but some parts of Pakistan are facing pollution worst than Delhi. Major concern is huge concentration of  particulate matter in the air.

Major contributing factors of Delhi's pollution are:

  • Inversion: Usually the temperature in atmosphere decreases with height, hence warmer air close to the earth surface move upwards and the air does not get stagnant. However during inversion cold air gets trapped close to surface overlain by a layer of warm air. This phenomena cap the movement of air. 
  • Wind pattern: In winter 72 % of wind blows into Delhi from northwestern part of India and Pakistan, these winds are not too strong during monsoon season. These wind brings particulate matter along with it.
  • Stubble burning: After harvesting paddy there is some left over on the ground which is called stubble. Farmers in Punjab and Haryana burn the stubble left out after harvesting the crops which is biggest contributor(70 percent) to the deterioration of air quality in Delhi. This stubble could be disposed effectively by using machines, but these machines does not comes for nothing. Farmer choose not to invest on these machines and simply burn the stubble. 
  • Industrial hubs: It is significant to mention that adjoining areas of Delhi are the industrial hubs therefore it probably result in the inflow of a mixture of coarse and fine continental pollutant aerosols.
Sudden increase in pollution is attributed to coincidence of all these factors. Stubble burning is followed by the northwestern winds blowing into Delhi. These winds bring with them smoke caused from stubble burning, and the pollution from industry. These all are assisted by the phenomena of inversion, which makes this toxic gas stagnant and city gets choked. 

This all happen usually on the onset of winter because at this time temperature is not sufficiently low to condense the water vapour and not sufficiently high to evaporate it. It is at that temperature at which it just trap the particulate matter and remain suspended in the atmosphere.


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