Characterization of dicarboxylates and inorganic Ions in Urban PM10 aerosols in the Eastern Central India

Size-segregated aerosol samples were collected continuously from July 2009 to June 2010 at urban area of Raipur, the eastern central India. The collected samples were analyzed for PM10 mass and its water-soluble dicarboxylate species and major inorganic ions. Results showed that the annual mean PM10 concentration was 270.5 μg/m3, which varied from 109.8 to 455.6 μg/m3. The higher concentration of PM10 mass was found during winter season followed by spring and summer, and lower during monsoon season. High PM10 mass concentration in Raipur could be attributed to the anthropogenic activities which may include high rate of construction activities, biomass combustion and mechanical erosion from road dusts. The concentrations of total dicarboxylates (TDCs) ranged from 325.3 to 1537.7 ng/m3 with an average of 904.0 ng/m3 constituting only 0.3% of PM10 mass. The oxalate (C2) and malonate (C3) were the dominant DCs followed by succinate (C4) and phthalate (Ph). The water-soluble major inorganic ions constituted 10.0% of PM10 mass with SO42- and NO3- being the dominant species followed by Cl- and Ca2+. The concentrations of dicarboxylates and major inorganic ions also showed maxima in winter and spring than summer and monsoon seasons. The ratio of malonate to succinate was used to distinguish primary sources from secondary sources of these dicarboxylates. The average C3/C4 ratio in spring and summer was 1.6 and 2.1, respectively, which suggested a large contribution of secondary sources to particulate dicarboxylates formation. Correlation analysis of DCs with SO42- and K+ was investigated to interpret their possible secondary formation pathways. Source identification study by principal component analysis (PCA) revealed that photochemical, secondary sources and vehicular emissions were the main sources contributing to overall PM10 mass with minor contribution from paved road dust and explained almost 95.5% variance of total aerosol data set. © Taiwan Association for Aerosol Research.