E-Paper
Pollutants enter Delhi via three distinct air corridors during winters: Study
Around 34% of the pollutants traced their origins to the Delhi-National Capital Region (NCR) and 18% from the north-western parts of the country.
Scientists have identified at least three distinct air corridors that act as carriers of pollutants to Delhi from places far and wide, including Nepal in the east, and Iran and Pakistan in the north-west, during winter, when the national capital’s air quality is at its worst.
The study -- the first real-time source apportionment analysis of Delhi, as the data was collected once every 30 minutes during two successive winters in 2018 and 2019 -- was conducted by a team of 15 researchers from the Indian Institute of Technology (IIT)-Kanpur; IIT-Delhi; Laboratory of Atmospheric Chemistry (LAC), Switzerland; Physical Research Laboratory; Ahmedabad; and Laboratoire des Sciences du Climat et de l’environnement, France.
The samples from the study were collected from the campus of IIT-Delhi.
“Contrary to the popular belief, we’ve found that pollutants enter Delhi through three distinct corridors during winter. While the north-west corridor primarily brings pollutants from Pakistan, Punjab and Haryana; Uttar Pradesh makes up for the north-east and the east; and Nepal, too, accounts for the east,” said SN Tripathi, head, civil engineering department, IIT-Kanpur, and one of the authors of the study.
A joint study -- conducted by The Energy and Resources Institute (TERI) and Automotive Research Association of India (ARAI) two years ago -- had shown that 64% of Delhi’s pollution is extraneous.
Around 34% of the pollutants traced their origins to the Delhi-National Capital Region (NCR) and 18% from the north-western parts of the country.
While 13% of pollutants were from other parts of south Asia and beyond.
The latest study showed that in each of these corridors, some specific chemicals were found in the air in much higher quantity, which suggested that certain industries were the worst polluters.
“Winds coming from the east were found to be carrying metals such as lead, copper and cadmium because of the presence of lead-based industries in the region. Similarly, elements such as selenium, bromine and chlorine were found to be predominant in winds blowing from the north-west sector. While selenium and bromine were found in industries dealing with drugs and chemicals among others, and chlorine emitted from brick kilns, landfill sites that burnt garbage and other factories,” he added.
The scientists detected at least 35 elements of which 26 were found in higher quantity than the rest, making up nearly one-fourth of the total mass of the coarser particles, known as particulate matter 10 (PM10).
“The study was a real-time source apportionment analysis, as the data was collected once every 30 minutes. We also found that Delhi is in the grips of pollution peaks twice daily. The first peak occurs between 3am and 8am the next one around 10pm,” said Dilip Ganguly, associate professor, Centre for Atmospheric Studies, IIT-Delhi.
Dr. Prashant Gargava, member-secretary, Central Pollution Control Board (CPCB), the country’s apex pollution control body, said: “This was a research & development (R&D) project, which was commissioned by the CPCB. It has provided some high-resolution data. We’ll analyse the data after we receive a complete report to utilise them for further policymaking decisions.”
“The study could open new vistas for air quality management in the country. Such studies will help us determine the presence of toxicity of each pollutant in the air and its harmful side effects. We need to conduct similar studies throughout the year to get a sense of the impact of pollution on Delhi,” said D. Saha, ex-head, air quality laboratory, CPCB.
