Chemical characterisation of fine aerosols in a smart city on the east coast of India: Seasonal variability and its impact on visibility impairment

Abstract

This study investigates the seasonal variation of PM (PM2.5 and PM10) over Bhubaneswar (20.3 degrees N, 85.827 degrees E), a smart city on the eastern coast of India. PM2.5 and PM10 ranged from 11.1 to 154.2 mu g.m(-3) and 20.4-273.8 mu g.m(-3), respectively. Carbonaceous (EC, OC, WSOC) species and water-soluble inorganic ions (WSIIs) were also examined for PM2.5 samples. SO42- ion was found to be most prevalent among all the species accounting to similar to 24% of PM2.5 mass, followed by OC (similar to 11%), NH4+ (10%), EC (5%), NO3- (4%), Na+ (4%), K+ (3%), WSOC (3%), Cl- (2%). The relatively low mean OC/EC ratio (1.9 +/- 0.4) and WSOC/OC (0.25 +/- 0.1) suggest the dominance of fossil fuel emissions over the study site. Additionally, for the first time in the eastern region, the role of several chemical species in light extinction coefficient (b(ext)) and visibility impairment is investigated using IMPROVE algorithm. The mean b(ext) is 311.5 +/- 141.8 Mm(-1) during the observation period, with a dominant contribution from (NH4)(2)SO4 followed by carbonaceous species (OM and EC). However, visibility levels sharply diminished by <9 km during winter than post-monsoon (<10 km), pre-monsoon (<19 km) and monsoon (<27 km) over Bhubaneswar.