Experts refute Kejriwal’s pollution statement

This Oct. 14, 2019 frame from a video shows shows paddy stubble burning in a field in Amritsar, Wednesday, Oct. 16, 2019.

This Oct. 14, 2019 frame from a video shows shows paddy stubble burning in a field in Amritsar, Wednesday, Oct. 16, 2019.   | Photo Credit: AP

‘Source apportionment studies have been done without machines’

Scientists and multiple experts refuted Chief Minister Arvind Kejriwal’s statement on Wednesday that no one is able to do source apportionment to find sources of pollution as no one has real-time source-apportionment machines.

The Chief Minister made the statement while he tagged a Central government-run agency’s data suggesting that stubble burning in neighbouring States is responsible for a maximum of 10% of Delhi’s pollution is “misleading” and reliant on “baseless guesses”. The Delhi government has been maintaining that the city’s pollution at this time of the year is mainly due to stubble burning in Punjab and Haryana.

A scientist from SAFAR said that the entire process is scientific.

“SAFAR takes into account the number of fires that is happening in Delhi’s neighbouring States from four different satellites and calculates the amount of PM2.5 based on it. We consider data from four satellites of which only two are Indian so that it will be more accurate,” the scientist told The Hindu.

“This data is fed to a Chemistry Transport Forecast Model, which is basically a software, that will take into consideration different factors such as wind speed, temperature and rain among others to find how much of the PM2.5 generated would reach Delhi,” the scientist added.

The scientist said that the model was developed in 2010 and has been in use since then.

Without machine

Anumita Roychowdhury, head of clean air programme at Centre for Science and Environment, said that several source apportionment studies have been done by different bodies, including IIT-Kanpur in 2015 and IITM (Indian Institute of Tropical Meteorology), without machines.

“It is done by collecting samples of ambient air and then doing chemical analysis. The analysis will show fingerprint and signatures of different sources such as vehicular pollution or stubble burning in the air. From it, we identify the sources,” she said.

Polash Mukerjee, Lead for Air pollution at the India Programme of the Natural Resources Defense Council, a US-based environmental advocacy group, also said that sources of pollution can be found both manually and using a machine.

“Both manually and using a machine, certain assumptions are used. When using a real time source apportionment machine, the chemical analysis will be done by the machine and it will give certain chemical traits of the sources. But it would not give the names of the sources,” he said.

Mr. Mukerjee said that the sources will have to be then identified manually.

Counter claim

Countering the Delhi government’s claim that the air pollution is mainly due to stubble burning in winter, Ms. Roychowdhury said, “In 2018 there were two peaks in air pollution in Delhi. One was around Diwali and the other was in December, when there was no stubble burning.”

To stress that the increase in pollution is due to stubble burning, the CM also said that the sources of pollution in Delhi has not changed much and hence the increase is due to stubble burning.

Both experts said that the same sources in Delhi can result in higher pollution concentrations during winter than summer. “In winter the wind speed will be less and the temperature will be less and the pollutants will not be dispersed as easily, and thus trapped, causing more pollution than in summer,” Mr. Mukerjee said.

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Printable version | Jul 7, 2020 3:05:18 AM |

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