Water Soluble Ions in PM2.5 and PM1 Aerosols in Durg City, Chhattisgarh, India

Abstract

This paper reports the atmospheric concentrations of PM2.5 and PM1 mass, water soluble inorganic components and their seasonal variations measured between the period of July 2009 and June 2010 in Durg city (20°23' to 22°02'N and 80°46' to 81°58'E), India. A cascade impactor sampler with Whatman 41 glass filters was used to collect aerosol samples in PM2.5 and PM1 size fractions. The results showed that the annual mean concentration of PM2.5 and PM1 were 135.0 µg/m3 and 64.7 µg/m3, respectively. Annual cycle shows highest concentration of PM2.5 and PM1 mass and water soluble ions in winter season and the lowest during rainy season. This is attributed to the enhanced production of aerosols and prevailing meteorological conditions. The higher PM1/PM2.5 ratio (0.48) during the whole campaign clearly indicates larger PM1 particle fractions were in PM2.5 at this location. Out of the total aerosol mass, water soluble constituents contributed an average of 11.57% (7.48% anions, 4.09% cations) in PM2.5 and 16.98% (11.14% anions, 5.85% cations) in PM1. The concentrations of SO42- and NO3- were highest in all size fractions and accounted for 32.76% and 13.38% of the total mass of the water soluble ions in PM2.5 and 32.78% and 12.21% in PM1 size fractions. Na+, Mg2+ and Ca2+, derived from the soil dust particles, were higher in spring and summer, as the dry weather in this season was favorable for the resuspension of soil particles. The seasonal variation of Cl-, K+ and secondary components (NH4+, NO3- and SO42-) were similar with high concentrations in winter and low concentrations in fall. Two principal components explaining 76.6% and 65.9% of the variance for PM2.5 and PM1 data set respectively were identified. Factor 1 has significant loading of species of anthropogenic origins and factor 2 showed partial associations with species of natural origins.