Real-time apportionment study up and running again in Delhi

Nov 16, 2023 04:44 AM IST

The data till 4 pm showed vehicles were the biggest contributor to PM2.5 in Delhi on Wednesday, accounting for 34% of pollutants.

The Delhi government’s real-time source apportionment study has been operationalised, with real-time data on the sources of pollution from PM2.5 particulates impacting the Capital now available on the R-asmaan portal (, officials aware of the matter said. The development comes a week after the Supreme Court directed the Delhi government to resume the apportionment study, around a month after it went dark..

Humayun's Tomb shrouded in smog in New Delhi on Wednesday morning. (Sanjeev Verma/HT Photo)
Humayun's Tomb shrouded in smog in New Delhi on Wednesday morning. (Sanjeev Verma/HT Photo)

The data till 4 pm showed vehicles were the biggest contributor to PM2.5 in Delhi on Wednesday, accounting for 34% of pollutants. Secondary inorganic aerosols — particles formed in the air as a result of gases reacting with each other from combustion sources — contributed 32% of Delhi’s PM2.5 concentration, and biomass burning was contributing around 26%, the data showed.

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Vehicles were also Delhi’s biggest contributor on November 14 and 13 – contributing 45% and 44% respectively. The contribution of biomass burning was 15% on November 14 and 14% on November 13, while secondary aerosols contributed 31% on November 14 and 14% on November 13%. Interestingly, the contribution of soil and road dust was particularly high – 15% — on November 13, but just 2% on both November 14 and 15.

The apportionment study looks at nine sources of PM2.5 particulates — secondary inorganic aerosols, road dust, vehicles, industries, construction, biomass burning, coal and fly ash, waste burning, and pollution from the residential sector. Unaccounted sources are placed in the “others” category.

It provides real-time data based on the chemical composition of the air, which is collected using filters, that is subsequently being assessed by a software model.

The Delhi cabinet approved the real-time source apportionment project in July 2021, with a memorandum of understanding (MoU) signed in October 2021 between the Delhi Pollution Control Committee (DPCC) and IIT Kanpur, which is executing this project. Real-time data was made available to the Delhi government from November 2022 onwards and to the general public from January 30 this year.

Last month, Delhi environment minister Gopal Rai had alleged that the apportionment study and the anti-smog tower at Connaught Place had been arbitrarily halted by DPCC chairman Ashwani Kumar, who had refused to pay the remainder of the amount pending to agencies running these projects. The Supreme Court on November 7 took suo motu cognizance of the matter and summoned Kumar, further asking the government for both projects to be promptly resumed.

On Wednesday, a senior DPCC official said the site of the apportionment study at Rouse Avenue was made operational the day after the Supreme Court’s orders, with real-time data reflecting on the website from the last couple of days. “The lab was made operational on November 8 and eventually, we began to collect data on all parameters, after sufficient enough data was made available through collection of gases,” said the official, adding that the pending amount of 2 crore due to be paid to IIT Kanpur, has also been cleared.

“The amount has been transferred and the lab is fully operational. It will share the day’s real-time data and hourly break-up too,” the official added.

The website is, however, still not showing the three-day forecasts on the contribution of sources expected in the coming days.

The apportionment study is different from the Decision Support System (DSS), under the Union ministry of earth sciences, which is an estimate-based model that estimating the sources contributing to Delhi’s PM 2.5 levels using meteorological conditions and a long-term emissions inventory from each sector.

Sunil Dahiya, analyst at the Centre for Research on Energy and Clean Air (CREA) said both models allow policy-based decisions to be made, with the apportionment study making use of a receptor-based model, that studies the chemical breakdown of PM 2.5. “This allows us to know at any given time what the biggest source is. This can allow the government to take focused action against a particular sector and once you have long-term data, policy decisions can be framed around the biggest contributors,” he said.

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