Biomass burning is behind Delhi’s poor air quality during winter, effect of Diwali fireworks does not last even a day: Finds IIT Delhi study

After the Supreme Court observed Diwali firecrackers as a temporary issue and held stubble burning a major responsible factor for poor air quality in Delhi, a latest research by the Indian Institute of Technology Delhi (IIT Delhi) has confirmed the same in its conclusions. Research performed by various scholars in different departments of IIT Delhi examined samples taken from different places in Delhi during the Diwali season and measured the proportions of various particulate matters in the air. The study revealed that biomass burning contributes the most to the air pollution of the national capital, and the pollutants from Diwali firecrackers don’t even remain in the air for a day. According to the research, biomass burning during winter includes stubble burning and burning of firewood etc for heat.

The title of the study is ‘Chemical speciation and source apportionment of ambient PM2.5 in New Delhi before, during, and after the Diwali fireworks.’ It has been published in Science Direct in Volume 13 Issue 6 (June 2022) of the Atmospheric Pollution Research journal of Elsevier BV. The authors and contributors of this research paper are from various departments of IIT Delhi. Chirag Manchanda and Mayank Kumar are from the Department of Mechanical Engineering. Vikram Singh and Mohammed Faisal are from the Department of Chemical Engineering. Naba Hazarika from the Department of Applied Mechanics has also participated in the research. Vipul Lalchandani, Ashutosh Shukla, and Sachchidanand Tripathi are the researchers from the Department of Civil Engineering who gave their inputs in this research study. Besides, the Geoscience Division of the Physical Research Laboratory of Ahmedabad is also an important part of the research team.

This study sheds light on the pollution sources impacting the ambient air quality in the capital before, during, and after Diwali. The researchers presented source apportionment results for highly time-resolved elemental and organic fractions of PM2.5 (Particulate Matter). The study was based in the National Capital Territory (NCT) Delhi and spans over 12 days from 20th October 2019 to 31st October 2019, with the Diwali festival on 27th October 2019. To account for the immediate effect of the firecracker burning, a six-day interval around the Diwali fireworks event was focused on. It was divided into three phases. Pre-Diwali (PD) (25th October 2019 24:00 IST – 27th October 2019 18:00 IST), During Diwali (DD) (27th October 2019 18:00 IST – 28th October 2019 6:00 IST), and Following Diwali (FD) (28th October 2019 6:00 IST – 31st October 2019 24:00 IST).

Samples were collected from two locations in Delhi during this period, The Indian Institute of Tropical Meteorology campus in central Delhi, and Indian Institute of Technology campus in south Delhi. The study used various instruments like Xact 625i Ambient Metal Monitor, multi-channel Aethalometer, High-Resolution Time-of-Flight Aerosol Mass Spectrometer to take precise measurements of pollutants in the air.

The study also took account of the established fact that though the emissions from the firecrackers contain carcinogenic factors, the health risks associated with the emitted species are primarily based on prolonged exposures at ambient pollutant levels. And in the case of firework events like Diwali, the duration of exposure is much shorter.

Other than firecrackers emissions, factors like vehicular pollution, industrial emission, coal combustion, dust particles, etc. are also taken into scope of consideration of this research and an attempt is made to ascertain how much does every one of them contributes to the sharp dip in the air quality of Delhi during that period of the year.

What researchers have found places biomass burning as the key contributor to the pollution. The conclusion of the research says, “The fireworks impact is most prominent at sampling sites only during the firecracker burning period that is the DD period. The coal combustion and dust-related sources mainly remained unaffected from the PD to the FD phase.” So it is evident that the effect of the pollutants from the firecrackers is there for a very limited time. “This study highlights that biomass burning emissions rather than the fireworks drive the poor air quality in the days following Diwali,” says the report in its abstract.

About the pollutants originating from biomass burning, the research paper concludes, “The biomass burning-related emissions rise steeply in the FD phase, and the average values increase by more than twice as compared to the PD phase. In terms of the source apportionment of the organic fraction, the primary organic emissions display a distinct rise in concentrations in the DD phase.”

The pollutants from firecrackers are different from those from biomass burning, therefore it is possible to identify the source of the pollutants. The study says that firecrackers mainly generate metallic elements, high levels of black carbon, and gaseous pollutants like carbon monoxide, along with oxides of sulphur and nitrogen. The study found that while the concentration of these elements peaked at around midnight on Diwali, their level plummeted to around one-third by the following day. The study also observed a rapid drop in Firecracker related PM2.5 level by 6 am the next day.

On the other hand, level of pollutants resulted from biomass burning remained high during the entire study period. In fact, the study says that biomass burning-related emissions rise steeply after Diwali, and the average values increase by more than twice as compared to the period before Diwali.

Chirag Manchanda, the lead author of this study, said, “The impact of the fireworks plummets within around 12 hours following Diwali.” Prof Vikram Singh, Department of Chemical Engineering, IIT Delhi, who was one of the investigators, said, “Both stubble burning and increased heating requirements of the region in winters drive the biomass burning activity.”

Prof Mayank Kumar, Department of Mechanical Engineering, IIT Delhi, said, “The result of this study provides crucial insights into a topic of long-standing debate and concern between air quality experts and policymakers committed to alleviating the extreme air pollution events in the capital of Delhi following Diwali.”

It is notable that on the occasion of the Diwali festival in the year 2021, the Kejriwal government in Delhi had issued a complete ban on firecrackers in the name of pollution control. While the Delhi Police initiated a crackdown on the sale and distribution of firecrackers this festive season after the Kejriwal-led government imposed a complete ban on the sale and bursting of all forms of firecrackers till January 1, 2022, the firecracker sellers had slammed the Delhi government’s reckless decision saying: “If Diwali will not be celebrated in India then do we expect it to be celebrated in Pakistan?”

The Supreme Court while hearing the firecracker ban case observed that the issue of firecrackers is a temporary issue and that the main matter is related to stubble burning. Now the research performed by IIT Delhi has bolstered the court observation with scientific evidence.

OpIndia Staff: Staff reporter at OpIndia