Meteorological Influence and Chemical Compositions of Atmospheric Particulate Matters in an Indian Urban Area
Shahadev Rabha, Binoy K. Saikia, Gyanesh Kumar Singh, Tarun Gupta
Abstract
Meteorological conditions essentially impact the emission, distribution, formation, and characteristics of particulate matter (e.g., PM2.5) in the atmosphere. In this study, sampling and chemical analysis of PM2.5 were carried out for about two winter months during December 2018 and January 2019 to determine their chemical components and possible emission sources in a Northeast Indian urban area (Jorhat). PM2.5 mass concentrations were observed to be varied from 81.65 to 193.34 μg m–3 with an average of 117.75 μg m–3, exceeding the permissible limit (60 μg m–3) of the National Ambient Air Quality Standards (NAAQS) of India. The average total water-soluble ions account for 12.27% of total PM2.5 mass, of which anions contributed up to 50.52% and cations contributed 49.48%. The correlations among the water-soluble ionic species indicate the formation of NH4NO3 and (NH4)2SO4 as major ammonium products with high ammonium concentration (30.73% of the total water-soluble aerosol mass) making the PM2.5 alkaline. A high concentration of acenaphthylene and naphthalene was also found out of the 16 US EPA poly-aromatic hydrocarbons (PAHs). The correlation study between the chemical components and the meteorological parameters pointed out coal and biomass burning as the main contributor to such high winter loading in Northeast India. Also, the formation of secondary organic carbon up to 21.84 μg m–3 was observed due to suitable meteorological conditions during winter.