Tuesday January 22, 2019
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To cut Delhi’s air pollution, pinpoint the source

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By Eric Dodge & Rohini Pande

This winter, Delhi’s government and the judiciary have implemented several policies aimed at cutting the national capital’s air pollution. The just-concluded odd-even scheme in the city required motorists to find alternative means of transportation every other day.

Car-free days, first in Gurgaon and then in Delhi, appeared to cause a temporary dip in pollution levels. The night hours when trucks can pass through Delhi have been reduced, and the National Green Tribunal has issued a direction to lower truck traffic coming into the city at night by levying an additional entrance fee.

On some days the air may be clearer. But what remains hazy is where Delhi’s air pollution comes from. Over the years, multiple attempts to find out – called source apportionment studies – have yielded contradictory results. There are numerous suspects: cars and trucks, smokestacks, farm fires in Punjab and Haryana, and dust from construction sites to name just a few. Without a better knowledge of the portion contributed by different sources, any policy response, no matter how bold, will be a little like a blind attempt to pin the tail on the donkey.

But that may be changing. The Indian Institute of Technology-Kanpur (IIT-K) has now released a major study, commissioned by the Delhi environment department in 2011. This promises to give the clearest picture of source apportionment yet. And other new sources of quality information on air pollution are appearing: the government has plans to add 10 new air quality monitoring stations in Delhi, and news outlets are setting up their own monitoring systems, including IndiaSpend #Breathe.

This could be a turning point in our understanding of the sources of Delhi’s deadly air, as well as our ability to craft smart policies that shut them down. We at Evidence for Policy Design (EPoD) are researchers who assist government ministries in formulating such responses. We think that at a time like this – a critical convergence of public concern, policymaker attention, and academic contribution – it’s worth taking stock of what we know now and how we came to know it. That clarity will make it easier to guide the discussion toward a policy response that will stick.

There are two ways of conducting source apportionment studies: direct sampling based on chemical analysis, and secondary data analysis based on monitoring data. The international best practice is to rely on receptor-based studies, but where budgetary constraints inhibit adequate sampling, analysis using secondary data may dominate.

Over the past 10 years, and excluding the just completed IIT-K study, we count 15 source apportionment studies that sought to pinpoint the sources of emissions and their respective contributions to Delhi’s overall air pollution. Ten are based on direct sampling; the other five rely on secondary data. While the main sources identified are similar across studies, the relative weights placed on different sources by these studies vary dramatically. This underscores both the difficulty of conducting them and the wide range in the quality of the studies currently available.

Getting a reliable picture of air pollution is inherently difficult due to Delhi’s changing weather conditions and constantly shifting patterns of emissions throughout the day, week, and year. Moreover, some of the most important pollution sources lie outside the National Capital Region. This makes it important that direct air sampling studies are broad enough to capture multiple sources and take samples at several different time points. An inability to do this-largely due to budgetary considerations-and the resulting differences in what gets sampled are an important part of the explanation for the large differences across studies.

In such situations, secondary data-based analysis may well be the best option for source apportionment studies, as long as these secondary sources are reliable and span relevant emission sources. Right now, we lack a measure of whether that is the case. Without standardized best practices about which secondary data sources to use and which model to use, source apportionment studies will continue to give conflicting results going forward.

So, we not only lack the best information on pollution, we also lack consensus on how to determine the second best. (IANS/IndiaSpend.org) (Photo: social.yourstory.com)

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Air Pollution in Delhi Again Reaches ‘Severe’ Levels

The India Meteorological Department (IMD) has forecast light rainfall at isolated places in Delhi over the weekend which might bring down pollution levels

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Air Pollution
Delhi air pollution again reaches 'severe' levels. Pixabay

Owing to a rise in humidity and light winds, the overall air quality of the national capital slipped to the ‘severe’ zone on Saturday, despite the authorities predicting it would remain in the ‘very poor’ category.

“Calm winds along with a spike in humidity levels because of an induced Cyclonic Circulation over Northern Plains are the major contributors for a hike in pollution levels in Delhi and adjoining areas,” Mahesh Palawat, Director at private weather forecasting agency Skymet told IANS.

He said that the pollution levels might increase in the coming days as humidity levels are expected to go up due to rains in Punjab, Haryana and Rajasthan.

“Around January 13 and 14, moderate to dense fog is expected to make a comeback, which will result in high pollution levels and minimums will see a drop by a couple of degrees,” he said.

However, the Skymet Director said that post January 15, the air quality might start improving due to cold, north-westerly winds which will blow over the plains of the country.

The System of Air Quality and Weather Forecasting And Research (SAFAR), in its daily pollution analysis, has been maintaining that the air quality in Delhi won’t go beyond the ‘very poor’ category.

Delhi. air pollution
A man rides his bicycle in front of the India Gate shrouded in smog in New Delhi, Dec. 26, 2018. VOA

On Saturday however, many areas in Delhi and adjoining areas at 12 p.m recorded ‘severe’ levels of toxic particulate matter (PM) 2.5.

Anand Vihar at 448, Dwarka sector-8 at 450, ITO at 413, Mundka at 438, Delhi University North Campus at 416, R.K. Puram at 415, and Wazirpur at 434 – all recorded ‘severe’ levels of PM2.5.

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Other areas like Jawaharlal Nehru Stadium, Ashok Vihar, Burari Crossing, Vivek Vihar, Sirifort, Okhla Phase-2 also fared in the same category.

On Wednesday and Thursday, Delhi-NCR witnessed its first better days of the year with the air quality recorded in the ‘poor’ zone.

The India Meteorological Department (IMD) has forecast light rainfall at isolated places in Delhi over the weekend which might bring down pollution levels. (IANS)