Chemical characterization of atmospheric particulate matter in Delhi, India, Part II: Source apportionment studies using PMF 3.0

World Bank reports Delhi as a second most polluted megacity in the world for particulates pollution. In this study, PM10 aerosol samples were monitored throughout 2008, documenting their characterization for major chemical elements and ions. To resolve complexity in source apportionment for these chemical constituents, UNMIX 6.0 and Positive Matrix Factorization (PMF 3.0) models were applied, resulting in the identification of four source factors. Factor-1, identified as the road-traffic source, showed a significant contribution (over 60%) to the receptor site, driven by strong temporal correlations among specific heavy metals. Factor-2, related to crustal origin, demonstrated substantial inter-relationships among common soil elements, indicating significant contributions to ambient air quality. Factor-3 was differentiated due to the contributions of secondary aerosols, while Factor-4 explained a specific chloride source with an 86% contribution. The findings serve as a benchmark for policymakers in understanding source apportionments in Delhi, highlighting critical factors affecting air quality and suggesting areas for further regulatory focus.