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| Photo by 2011CIAT/NeilPalmer |
Every winter Delhi is covered in a thick blanket of smog, increasing the risk of health problems for the city's residents. The AQI in winter reaches the severe end of the pollution spectrum. Even though the Delhi air pollution is pretty much harmful throughout the year, the literal visibility of the pollution in Delhi's chilling winter shakes people out of slumber to demand action from the government. And it is not only the capital city of Delhi but many other big Indian cities, especially in the northern part of the country, which are facing the brunt of air pollution. What are the contributing factors to the dire situation of air pollution in Delhi?
Vehicular emissions
Delhi has seen its vehicle population increase by 21 times from 1981 to 2021. Currently, the capital city of Delhi host over 13 million registered vehicles in addition to the traffic that the city receives from various part of the country on the daily basis and is responsible for more than 24 per cent of particulate pollution during winter months along with other toxic gases like carbon monoxide, nitrogen oxides, photochemical oxidants, etc. Out of these, PM2.5 is one of the most dangerous constituents of pollution coming out of motor vehicles' tailpipes, which has been known to cause cardiac and respiratory problems and is identified as a 'carcinogen' by WHO.
With the growing population and urbanization in the wake of economic development, Delhi's air pollution is only going to aggravate in the future if reformative steps are not taken.
Industrial emissions
Gurgaon-Merrut-Delhi is one of the major industrial regions in the country covering an area of 51.81 square km. Delhi itself has 24 industrial areas as tabulated by the Labour Commissioner of Delhi on their website. Along with it, National Capitol Region (NCR) contains various industrial clusters in the adjoining states of Rajasthan, Haryana, and Uttar Pradesh, which majorly host industries related to Chemical, metal, textile, and pharmaceuticals, and coal is one of the major fuel used in these industries, according to one estimate these industries uses 1.7 million tonnes of coal annually.
These industrial emissions contribute to Delhi's air pollution in terms of adding particulate matter (PM), Sulphur Dioxide, and nitrogen oxide into the atmosphere. A study conducted by TERI-ARAI in the year 2018, pegged the contribution of industries in particulate matter (PM) pollution in the range of 27-30 per cent.
The last made industrial policy available on the website of the Department of Industries of the Delhi government is from 2010, which provides very few guidelines for the pollution mitigation of industries.
Power plants
At the time of independence, India's total power generation capacity was 1.3 GW, which provided power to only 0.5 per cent of the population. By the end of 2022, power generation has reached a total capacity of 407 GW, which has made electricity accessible to more than 97 per cent of the population of India. This journey of powering India has been mainly driven by coal, which today contributes to 50 per cent of power generation and hence, is now a big contributor to air pollution.
Delhi, burdened with a huge population and power needs, has six power plants two of which are coal-based and the other four run on gas. Coal takes care of almost 33 per cent of the power needs of Delhi. Other than this there are 13 power plants with a capacity of 11,000 MW within a radius of 300 km of Delhi.
Coal when burned in power plants for energy emits particulate matter (PM), sulphur dioxide (SO2), and nitric oxide (NO), which are major constituents of Delhi's air pollution. Most of it is emitted by coal-based power plants, like the Badarpur power plant which according to a study by CSE is only 30 per cent efficient and has outlived its life with an age of 30-40 years. Winds also bring the emission from the other power units in the vicinity of the capital city of Delhi.
Agriculture waste burning
Agriculture in the adjoining states of Punjab and Haryana is largely based on the Rice-Wheat cropping sequence (RWCS), farmers grow these two crops in rotation. Rice cultivation is done in the monsoon season with harvesting done during October-November and after that, the climate is ripe for wheat cultivation.
The modern harvester used for rice harvesting leaves almost all the plant straw rooted in the soil, which is called stubble. After rice harvesting farmers are left with a very small window of time to remove this agricultural residue and sow new wheat seeds. The removal of this residue is labour intensive, and if done with a machine, cost quite a lot to the farmer, hence the easiest and cheapest way he deals with it is by setting it to fire.
The IARI study estimates that in 2008-09, crop residue burning released 149.24 million tonnes of carbon dioxide (CO2), over 9 million tonnes of carbon monoxide (CO), 0.25 million tonnes of oxides of sulphur (SOX), 1.28 million tonnes of particulate matter and 0.07 million tonnes of black carbon and all of these contribute heavily to the air pollution. With the winds, these pollutants spread all over northern India with the maximum impact felt in Delhi.
All of Delhi gets covered in black soot during this period which gets aggravated due to stagnant wind conditions and temperature inversion.
Weather condition/ Temperature inversion
With a whole host of pollution-contributing factors in place, the weather condition, especially during winter, make the situation much worse to the point where AQI cross its maximum limit and the government have to shut schools.
With the onset of winter a phenomenon called temperature inversion takes place, where due to the cold weather and already existing pollution in the air, the sun's rays do not sufficiently heat up the surface which causes the cold air to trap near the surface with a lid of hot air above. With no wind blowing these conditions make the air stagnant and trap the soot-laden polluted air caused by stubble burning. This condition acts as a catalyst to aggravate Delhi's air pollution during winter months.
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Delhi air pollution