Chemical, microstructural, and biological characterization of wintertime PM2.5 during a land campaign study in a coastal city of eastern India

Abstract

Bhubaneswar is a rapidly developing city in the eastern coast of India. Previous studies are evidence of the importance of its location for understanding the outflow of pollutants from mainland India into the Bay of Bengal, specifically during the winter. Therefore, we present the characteristics of PM2.5 (particulate matter with aerodynamic diameter < 2.5 μm) collected during a land campaign between November 2014 and January 2015 (representing the winter). Gravimetric measurement of mean PM2.5 was in the range of 101–142 μg/m3 at different locations that was approximately 65–135% higher than the 24 h average National Ambient Air Quality Standards (NAAQS). Spectrometric measurement of PM2.5 and PM1.0 depicted a typical diurnal pattern with distinct morning and evening peaks, confirming similar source contribution and a higher accumulation mode PM over the traffic location. For example, 85.7, 79.1, 80.6, and 84.8 % of PM1.0 contributed to PM2.5 at reference, residential, industrial, and traffic sites, respectively. Chemical characterization and Positive Matrix Factorization (PMF) indicated four most probable sources of PM2.5 with major contributions from vehicular emissions (32.2 %), followed by industrial (25.8 %), combustion (coal, oil, and biomass burning at 22.4 %), and crustal sources (19.7 %). Enrichment factors and mass closure analysis supports this observation. Microstructural analysis broadly classified the PM2.5 particles into four categories. For the first time Endotoxin concentrations in ambient PM2.5 (0.021 ± 0.022 EU/m3) were quantified as a step ahead to understand the biological composition of PM. Heavy metals detected in PM2.5 were used to perform an excess cancer risk assessment.