Air Quality in India
Air pollution in South Asia - especially across the Indo-Gangetic basin in Northern India, Pakistan, Nepal, and Bangladesh - ranks among the most severe in the world. In India alone, hundreds of millions of people are exposed to PM2.5 concentrations an order of magnitude greater than World Health Organization guidelines. However, fundamental aspects of our understanding of particle air pollution in India are incomplete. To inform policies to reduce exposures and improve public health, we are investigating the emissions and physicochemical processes that affect particle concentrations and composition. Our research includes field- and laboratory-based experiments and modeling studies.
Ambient fine particulate matter (PM2.5) levels in Delhi, India rank among the highest levels routinely measured in any city in the world. Annual average PM2.5 concentrations in Delhi are roughly 150 µg m-3, or about 15 times higher than WHO guideline concentrations, and respectively 8× and 1.5× higher than levels in Los Angeles and Beijing. High PM2.5 levels in Delhi are driven by a combination of unfavorable local meteorology and an unusually diverse mixture of local sources. PM sources in the Delhi area are numerous and incompletely understood, but include light- and heavy-duty vehicle traffic emissions and associated road dust, solid fuel combustion for heating and cooking, biomass and waste burning, thermal power plants, diesel generators, construction, and small-scale local industries (e.g., brick manufacturing).
Current research topics include: (i) chemical composition and source apportionment of ambient air pollution in Delhi, Bangalore, and across the Indo-Gangetic Plain, (ii) mobile monitoring to characterize pollution at high spatial resolution in Bangalore, and (iii) exploration of lower-cost sensing technologies for characterizing ambient air pollution.
A regional challenge
Evidence from satellite remote sensing demonstrates that more than 99% of India's population lives in areas that exceed WHO PM2.5 air quality guidlines, and for hundreds of millions of people concentrations exceed the guideline by 10×. Major cities and rural areas alike are extremely polluted, indicating the importance of both primary emissions sources and regional atmospheric chemistry.
Perspective Piece: Apte JS and Pant P. 2019. Towards cleaner air for a billion Indians. Proceedings of the National Academy of Sciences 116, 10614-10616. [link]
Delhi Aerosol Supersite
In collaboration with the Indian Institute of Technology, Delhi, we are investigating the sources and chemical composition of the ambient submicron aerosol (PM1) in South Delhi. Our online measurements consist of particle number size distributions (via scanning mobility particle sizer), black carbon concentrations (via aethalometer) and non-refractory PM1 composition (via Aerodyne aerosol chemical speciation monitor), all collected at 1-5 minute frequency. Using positive matrix factorization (PMF) receptor modeling, we are investigating the local and regional sources that contribute to Delhi's high background concentrations of PM1. Our measurements have been online since January 2017, with the intention of providing a long-term record of air pollution changes in Delhi over the coming years.
What's polluting Delhi's air?
Detailed measurements of aerosol chemical composition provide insight into the sources and atmospheric processes that govern air pollution in Delhi.
S. Gani et al, 2019. Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study. Atmos. Phys. Chem. [open access]
S. Bhandari et al., 2020. Sources and atmospheric dynamics of organic aerosol in New Delhi, India: Insights from receptor modeling. Atmos. Phys. Chem. [open access]