Why real-time source apportionment data could help Delhi combat air pollution

In its MoU, which was signed with IIT Delhi, IIT Kanpur, TERI and IISER Delhi, the government specified the need to identify real-time sources of pollution

By summer next year, Delhi could start receiving monthly and daily data on the biggest sources of pollution plaguing the capital on any given day, with a real-time source apportionment study being sanctioned by the Delhi government in October this year. In its Memorandum of Understanding (MoU), which was signed with IIT Delhi, IIT Kanpur, the Energy and Resources Institute (TERI) and IISER Delhi – the government specified the need to identify real-time sources of pollution so corrective action could be taken across the most polluting sectors on each day. Experts say once daily reports begin, this could not only indicate how successful corrective measures have been, but also which sectors require the most action in the long-term.

Experts say once daily reports begin, this could not only indicate how successful corrective measures have been, but also which sectors require the most action in the long-term (Arvind Yadav/HT Photo)

Delhi in the past five years has seen two source apportionment studies being carried out by IIT Kanpur (2016) and TERI (2018) in order to identify the contribution of each sector in Delhi’s pollution load. Neither of these, however, gave real-time data, instead, identifying Delhi’s sources of pollution over a two-year period.

Anumita Roychowdhury, executive director, research and advocacy at the Centre for Science and Environment (CSE) says the problem with such studies is that by the time they are completed and a policy decision is made, there could be a change in the contribution of each sector.

“We have seen source apportionment studies in the past, but both studies gave slightly different results. While this may be down to the methodology, but there is a chance that it could also be due to a slight change in the source contribution over a period of time. A real-time study meanwhile will give you figures each day and one can analyse the average and daily trends from each sector, according to which both short-term and long-term action can be tailored,” says Roychowdhury.

She said that on a day when dust pollution is the biggest source of pollution, sprinkling of water makes sense instead of doing it throughout the winter, whereas if the vehicular sector is regularly emerging as the biggest contributor, a long-term plan on the vehicular sector may have to be devised.

Professor Mukesh Sharma from IIT Kanpur, who is part of the team that is working on the real-time source apportionment project, said once operational, the equipment being set up in Delhi will be able to not only give an emissions inventory – the total contribution load from each sector, but also provide short-term forecasting for these sectors.

“We will be able to give in percentage and absolute terms the contribution from each sector at any given time. It will be shared with the government similar to the day’s air quality index (AQI) is shared and not only will this give clarity to the government, but will also educate the public,” Sharma said.

He said machines currently are being procured and imported, with the first monthly report expected to be released around the months of May or June. “It may become fully functional just before next winter,” he added.

Karthik Ganesan, Fellow and Director, Research Coordination at the Council on Energy, Environment and Water (CEEW) says real-time source apportionment can be a welcome addition to the existing body of knowledge and also establish a precedent for the use of the associated technology and methods to assess air-quality in Indian cities. However, he believes action can still be taken without such a study.

“This will probably be much more useful when we are pushing for a reduction in air pollution to levels below the current National Ambient Air Quality Standards (NAAQS) but if you have to take action, we already know sources of pollution which need to be regulated. Pollution from industrial stacks in neighbouring states, pollution from non-compliant vehicles, rampant and illegal dumping of construction and demolition debris in public land, poor construction practices and waste burning on a large scale – all are sources which can be fixed with the evidence that is at already hand,” said Ganesan.

PAST STUDIES

In the two past studies to assess sources of pollution for Delhi, the transport sector, biomass burning and industries had emerged as the biggest sources of pollution in the region.

In the IIT Kanpur source apportionment study, biomass burning (26%) was identified as the primary source of PM 2.5 pollution in the winter, followed closely by vehicles (25%). However, it also stated secondary pollutants (30%) -- formed in the air when pollutants and gases mix, made up a huge chunk of PM 2.5 in the winter.

“The winter sources include secondary particles (25 - 30%), vehicles (20- 25%), biomass burning (17 – 26%), municipal solid waste burning (9 - 8%) and to a lesser extent soil and road dust. It is noteworthy, in winter; major sources for PM10 and PM2.5 are generally the same,” IIT Kanpur had said in its study.

TERI’s study had meanwhile identified industries (30 per cent), which included thermal power plants as the biggest source of PM 2.5 pollution in winters, followed closely by vehicles (28%). It however identified the geographical contribution of Delhi to its own PM 2.5 share to be just 36% in winters, with 34% coming from NCR towns. The remaining 30% arrives into Delhi from upwind regions that are outside NCR, including transportation of dust from the middle-east.

“The average contribution of Delhi’s own emissions in Delhi’s PM2.5 concentrations was found to be 36% in winters and 26% in summers,” said TERI’s 2018 study.

Dipankar Saha, former head at CPCB’s air laboratory says not only is it important to determine the biggest sources of pollution, but also the impact meteorological conditions can have.

“We may see the contribution of some sectors remaining low during a particular period and suddenly spike. It is therefore important to analyse a slightly long-term trend and to factor meteorological conditions, such as wind speed, which may show reduced data from certain sectors. However, this data cannot remain hidden in the long-term. Similarly, action plans can be formed for the biggest sources of pollution in each season. We already know dust is the biggest contributor during summers, but sprinkling of water is rarely done during that period,” Saha said.