The deteriorating air quality and suffocating smog have led to closure of primary schools in Delhi.
What are the causes?
Smog - Smog refers to a smoky fog (smoke+fog) and is a kind of air pollution.
Fog is a hazy condition which is a result of suspension of water droplets close to the ground.
Smog, on the other hand, is a mixture of pollutants in the atmosphere which consists of fine particles and ground level ozone.
When pollution is high, nitrogen oxides and dust particles interact with sunlight to form ground-level ozone, leading to hazy smog.
This condition is a result of a range of factors including:
geography of the place.
sunlight
calmness of winds.
post-harvest crop burning.
firing of brick kilns.
dust from construction sites and unpaved roads.
vehicular pollution.
domestic and industrial emissions.
Wind - Smog occurs in a location that is far away from the actual source of pollution after the hazardous pollutants have drifted away in the wind.
Delhi experiences two kinds of winds in winter which are:
wind carrying pollutants from stubble burning in Punjab.
wind bringing in moisture from Uttar Pradesh.
These two winds collide in the upper atmosphere above the region.
However, Delhi and its neighbouring areas have nearly still wind conditions near the ground, which is due to prevailing anti-cyclone conditions around the region during winter.
The two winds, combined with the near still wind conditions, effectively trap the pollutants leading to persistent smog.
Crop burning - The smog that envelops the region is exacerbated by the burning of biomass in nearby Punjab and Haryana.
The post-monsoon burning of rice and wheat residue releases maximum aerosols.
And this contributes to the volume of PM2.5 in the air.
What should be done?
The Delhi government has taken various measures in the past including:
the ban on Deepavali crackers.
shift to compressed natural gas for commercial vehicles.
restricting car use to odd and even number plates on alternate days.
However, air quality index has touched extremely hazardous levels in some parts of Delhi, turning into a public health emergency.
The burden of such chronic problems has outweighed the benefits conferred by the above measures.
Therefore, besides these minor corrections, the Centre and States must urgently address farm residue burning in north India.
A workable solution demands a coordinated effort from the governments of Delhi, Punjab, Haryana and Uttar Pradesh, assisted by the Centre.
Delhi’s unique weather conditions require a comprehensive, well informed solution to the pollution crisis.
Quick Fact
Particulate matter (PM)
PM or particle pollution is a mixture of small particles including black carbon, mineral dust, sulphate, nitrates, ammonia, sodium chloride, and liquid droplets in the air.
WHO classifies particulate matter into two broad types - PM10 and PM2.5, indicating the diameter of the particles in microns.
Chronic exposure to both PM10 and PM2.5 can lead to cardiovascular and respiratory diseases, as well as lung cancer.
PM2.5 can cause skin diseases and reduction in life expectancy. It can cross into the blood, causing damage in many organ systems, .
In Delhi, the ground-level ozone and PM 2.5 play a significant role in formation of smog.
