Wintertime oxidative potential of PM over a big urban city in the central Indo-Gangetic Plain.

Indo-Gangetic Plain (IGP) experiences a heavy load of particulate pollution impacting the 9 % of the global population living in this region. The present study examines the dithiothreitol (DTT) assay-based oxidative potential (OP) of PM and the major sources responsible for the observed OP over the central IGP (Kanpur) during winter. The volume normalized OP (OP) of PM varied from 2.7 to 10 nmol DTT min m (5.5 ± 1.5) and mass normalized OP (OP) of PM varied from 19 to 58 pmol DTT min μg (34 ± 8.0), respectively. Major sources of PM were identified using the positive matrix factorization (PMF) and the contribution of these sources to observed OP was estimated through multivariate linear regression of OP with PMF-resolved factors. Although the PM mass was dominated by secondary aerosols (SA, 28 %), followed by crustal dust (CD, 24 %), resuspended fine dust (RFD, 14 %), traffic emissions (TE, 8 %), industrial emissions (IE, 17 %), and trash burning (TB, 9 %), their proportionate contribution to OP (except SA) was different likely due to differences in redox properties of chemical species coming from these sources. The SA showed the highest contribution (23 %) to observed OP, followed by RFD (19 %), IE (8 %), TE & TB (5 %), CD (4 %), and others (36 %). Our results highlight the significance of determining the chemical composition of particulates along with their mass concentrations for a better understanding of the relationship between PM and health impacts. Such studies are still lacking in the literature, and these results have direct implications for making better mitigation strategies for healthier air quality.