Chemical characterization and source apportionment of fine particulate matter (PM2.5) at a rural site in north central India

Abstract

Characterization of PM2.5 (fine particulate) matter was conducted at Sikandarpur (27.26 °N, 78.00 °E), a rural site in North Central India in summer (April 2015 to June 2015) and winter (December 2015 to February 2016) seasons. PM2.5 mass and concentrations of major water-soluble inorganic ions (WSIIs: Cl-, SO42-, NO3-, Na+, NH4+, K+, Mg2+ and Ca2+) were determined. PM2.5 mass was categorized into 3 levels: <60, 60-100 and >100 µg m-3 (average = 88.7±27.2 µg m-3). Correlation analysis of secondary inorganic species (SO42-, NO3- and NH4+) showed the existence of (NH4)2SO4, NH4NO3 and NH4Cl, which were more predominant during winter season when NH4+ concentrations were high. During winter, the concentrations of SIA (secondary inorganic aerosol) were influenced by local air masses. Clusters of backward air mass trajectories were simulated from HYSPLIT Model which revealed three clusters and originated from various directions and source regions. Clusters 1 and 3 showed the impact of air masses from local sources while cluster 2 was mainly influenced by long range transport. Positive matrix factorization (PMF) was employed for source apportionment. Three factors were isolated as potential sources: soil dust (42.3%), combustion (26.3%) and secondary aerosol formation (31.4%), respectively.