Air pollution in Delhi and the whole of the Indo-Gangetic Plains is a complex phenomenon that is dependent on a variety of factors. But, every year in October, Delhi’s air quality starts to dip.
Factors responsible for this:
1. Withdrawal of monsoons:
During monsoons, the prevalent direction of wind is easterly. Once monsoon withdraws, the predominant direction of winds changes to north westerly. During summers, too, the direction of wind is north westerly and storms carry dust from Rajasthan and sometimes Pakistan and Afghanistan.
2. Dip in Temperatures:
As temperature dips, the inversion height — which is the layer beyond which pollutants cannot disperse into the upper layer of the atmosphere – is lowered. The concentration of pollutants in the air increases when this happens.
3. High-speed winds:
They are very effective at dispersing pollutants, but winters bring a dip in wind speed over all as compared to in summers.
4. Farm fires:
A 2015 source-apportionment study on Delhi’s air pollution conducted by IIT-Kanpur also states that 17-26% of all particulate matter in Delhi in winters is because of biomass burning.
5. Dust pollution:
Dry cold weather means dust is prevalent in the entire region, which does not see many rainy days between October and June. Dust pollution contributes to 56% of PM 10 and and the PM2.5 load at 59 t/d, the top contributors being road 38 % of PM 2.5 concentration.
6. Vehicular pollution:
It 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.
Measures to improve air quality:
- Improving public transport
- Limiting the number of polluting vehicles on the road
- Introducing less polluting fuel
- Strict emission regulations
- Improved efficiency for thermal power plants and industries
- Moving from diesel generators to rooftop solar
- Increased use of clean renewable energy
- Electric vehicles
- Removing dust from roads
- Regulating construction activities
- Stopping biomass burning, etc.
Sources: Indian Express.