Burning of twigs, dry leaves for warmth & vehicles biggest pollutants in Delhi, shows study

Biomass burning, vehicular emissions & dust were other major sources of PM2.5 in December, says Real Time Source Apportionment Study. Industrial pollution was comparatively less.

File photo of smoke rising from burning of plastic garbage near Mundka in Delhi | ANI

New Delhi: With the stubble burning season far over, open burning of garbage besides twigs and dry leaves for ‘warming purposes’ has emerged as one of the major sources of air pollution in Delhi, apart from construction and transport activities, according to the newly-initiated ‘Real Time Source Apportionment Study’.

Industrial pollution was comparatively lower than other months, it says.

The Delhi Pollution Control Committee (DPCC) in collaboration with IIT-Kanpur, IIT-Delhi and The Energy & Resources Institute (TERI) are undertaking this project which is being led by Prof Mukesh Sharma from IIT-Kanpur.

An MoU was signed between IIT Kanpur and DPCC in October 2021, to kickstart the project. But the study, meant to identify sources contributing to the air quality of Delhi-National Capital Region (NCR) in real-time to understand the air pollutants in the city and reduce them accordingly, only began on 23 December 2022.

The initial findings for December concluded that secondary inorganic aerosols, which travel long distances, contribute to a large proportion of the air pollution mix. Biomass burning (wood, stubble, etc.), vehicular emissions and dust (road and construction) were the other major sources of PM2.5 in the last one month, the study said.

Concurring with the findings, an official of the DPCC said that fires being lit for the purpose of warming is adding majorly to the air pollution.

“One of the biggest pollution sources currently is the burning of twigs and dry leaves for warming purposes. The stubble season is already over on 30th November. So, its effect is not so much now. It has been replaced by waste combustion/ burning of waste to keep warm. The pollution from industries has not been found to be as severe as other factors stated. The pollution from construction activities, however, has been quite high,” said a DPCC official.

DPCC also told ThePrint that air pollution was “dynamic” and not one source will be dominant since it keeps on changing every hour. For instance, in the morning (from 9 am to 11 am) and evening (from 6 pm to 8 pm), the contribution of vehicular pollution will be more, whereas biomass burning will be causing the most pollution during the night.

Delhi is in the grip of severe cold while the meteorological office has said air quality will be in the very poor category for the next two-three days.

In such a scenario, the ‘Real Time Source Apportionment Study will be aiding the administration in its efforts to check air pollution. Chief Minister Arvind Kejriwal himself had said that IIT Kanpur’s real-time source apportionment study is helping Delhi with pollution-related data in a proactive manner.

According to the Delhi government’s statement, Kejriwal suggested that IIT-Kanpur should try to provide a more detailed analysis of the real-time sources, such as the type of vehicles causing pollution at different times, and specific areas where biomass, including garbage, is being burnt.

But sources in the Delhi government said that while they can find out a rough estimate of the proportion of emissions of sulphur and nitrogen oxides from BS I, II, III and IV vehicles, more granular identification may be a little difficult. The study’s objective, they said, was also not to focus on specific polluting transport but on whether the transport sector is complicit in causing pollution.

In the past, there were source apportionment studies that “played an instrumental role in describing the variety of sources that contribute to air pollution in Delhi-NCR but their “estimates differed significantly” making the “determination of exact sources uncertain and air quality improvement measures ineffective”, the sources said. But it is acknowledged that multiple-year inventories may capture the dynamic nature of air pollution and enable more accurate and real-time information.

What the project entails

As for the project, it has two main components of a ‘supersite’ and a mobile lab which will cover 13 pollution hotspots in Delhi. The hotspots where pollutants such as sulphur oxides, nitrogen oxides, ozone will be monitored are Jahangirpuri, Anand Vihar, Ashok Vihar, Wazirpur, Punjabi Bagh, Dwarka Sector 8, Rohini Sector 16, RK Puram, Bawana, Mundka, Narela, Okhla Phase II and Vivek Vihar.

While the supersite to help forecast air pollution levels on an hourly, daily, and weekly basis has come up at Rouse Avenue, the mobile lab is still in its initial stages, officials told ThePrint.

“Real Time Source Apportionment Study gives a set of concentrations of pollutants from different sectors over a period of time. It is not limited to a particular time. The process will run automatically. So, you will know the air quality today and tomorrow, and can see whether the intervention measures taken to address those pollutants have worked or not,” said a TERI scientist, who has worked on the project. “Similarly, for forecasting, with the data available you will be able to estimate the level and sources of pollution for the next 10 days.

While TERI will estimate the emission inventory (the detailed evaluation of the number of air pollutants discharged over a period of time), the data will be fed into IIT-Delhi’s ‘modelling exercise’ to assess the level of concentration of particulate matter like PM10 and PM2.5. IIT-Kanpur is overseeing the overall coordination of all activities of the project.

“If you say, for instance, ambient air quality outside my building is 100 micrograms per cubic metre. This is the value. Now, the study will determine how much is coming from the transport sector, industries, service sector, construction activities and so on. This information will be made available to the Delhi government, and it can decide what proactive steps to take to curb pollution,” the TERI researcher said.

Sunil Dahiya, an analyst at Centre for Research on Energy and Clean Air (CREA), said such technologies are useful in terms of curbing pollution levels if clubbed with the forecasting systems as well as the CAQM because real-time actions can be taken in issuing directions to shut down certain industries or other sources of pollution.

In case five thermal power plants are shut down because they were found to be a polluting menace, then it can be observed whether the real-time interventions helped reduce the contribution from the power sector, he said.

“This doesn’t mean that all other cities should adopt it. Because even if we don’t have these kinds of studies, it will not be a big problem since we already have enough research to know what the basic sources are. We know fossil fuels or the anthropogenic consumption of fossil fuels, be it in the transport sector industries or power generation, are the main culprits,” he told ThePrint.

“Unless their consumption comes down, or emission load from those sectors comes down, we will not be able to breathe clean air.”

Dahiya added it was imperative that the study’s findings and status be made publicly available because there have been instances in the past in Delhi where attempts were made to do something similar but stopped somewhere. Since there was not much transparency or information available in the public domain, there was no way to ascertain what were the reasons or whether they performed well or not, he pointed out.

(Edited by Tony Rai)