What is polluting Delhi’s air? A study on Delhi’s air quality conducted by IIT-Kanpur over two years has revealed that vehicle exhaust chokes our lungs in winter. In summer, it is the fumes from the coal-fired power plants, the fly ash they release and dust from roads and construction sites.
IIT-Kanpur recently submitted the first draft of its “source apportionment study” commissioned by the Delhi environment department in 2011 to understand the causes of air pollution in Delhi so that suitable action could be taken. The final report is expected soon.
“Source apportionment studies helps in identifying the exact source of pollution and the extent of its contribution. The study has covered pollution in both summer and winter and has been done by monitoring air quality in north, south, east, west and central Delhi between August 2013 and September 2015,” a senior environment department official told Hindustan Times.
The draft, according to Delhi Pollution Control Committee sources, said that in winter vehicular emission and secondary particulates (particles that form in the atmosphere from other gaseous pollutants, particularly sulphur dioxide, nitrogen oxides, ammonia, and volatile organic compounds) constitute 60% of the pollutants. Around 30% is caused due to biomass, garbage and leaf burning. The remaining is dust.
“In summer, however, coal and fly ash contribute around 30% while road and construction dust cause 25% pollution. Vehicles and secondary particles contribute 25% while garbage, leaf, crop stubble and dried cow dung burning another 18%,” said a DPCC official. This is the first-of-its-kind study done specifically for Delhi.
Environment department officials said combating air pollution was quite difficult in the absence of a clear policy framework and this study, once finalised, would help frame a policy for a city.
The study focused on what had caused the rise of pollutants such as sulphur dioxide, suspended particulate matter and nitrous oxides. It studied how industries, vehicles, burning of waste and leaves and construction dust contributed in increasing the air pollution.
“Earlier studies didn’t focus on secondary particles. Primary sources cause particle pollution on their own, while secondary sources let off gases that can form particles after reacting with the atmosphere. Power plants and coal fires are examples of secondary sources,” a DPCC official said.
The last such study was done by the environmental information system (ENVIS) of the Centre of the Indian Institute Of Tropical Meteorology (IITM) in 2010, which shows the emission contribution of different sectors.
Anumita Roy Chowdhury, executive director of Centre for Science and Environment, said this clearly brings out the impact of vehicles on the air quality of the city.
“While all sources are important, the significance of vehicular pollution is to be seen. In winter, it is the biggest polluting source. In summer, even though the impact of dust gets higher, you have to keep in mind that this road dust can also carry the vehicular emissions and create a deadlier cocktail,” Roy Chowdhury said, adding that an action plan may now be possible with source-wise measures ensuring cleaner air in the city.