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Water-soluble ionic composition of PM2.5–10 and PM2.5 aerosols in the lower troposphere of an industrial city Raipur, the eastern central India

Research paper by Dhananjay K. Deshmukh, Manas K. Deb, Yukio Suzuki, Giorgos N. Kouvarakis

Indexed on: 12 Jul '11Published on: 12 Jul '11Published in: Air Quality, Atmosphere & Health



Abstract

Size-segregated aerosol samples were collected at Raipur, India, during the period of October 2008 to September 2009, using eight-stage cascade impactor-type aerosol sampler at a flow rate of 28.3 l/min. The results give information about the mass concentrations, seasonal variations, and sources of water-soluble inorganic species viz. Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO3-, and SO42- in both PM2.5–10 (coarse) and PM2.5 (fine) fractions. Annual mean of mass concentrations of PM2.5–10 and PM2.5 aerosols were monitored to be 200.7 ± 55.1 and 185.9 ± 66.9 μg/m3, respectively. The annual mean concentrations of the inorganic components were monitored to be 5.4 ± 2.4, 6.2 ± 4.7, 5.3 ± 1.8, 3.2 ± 0.46, 40.8 ± 7.9, 9.2 ± 3.8, 21.6 ± 5.5, and 17.9 ± 4.0 μg/m3 in PM2.5–10 aerosols and 4.1 ± 2.1, 13.4 ± 4.2, 7.7 ± 2.0, 1.7 ± 0.4, 18.7 ± 5.4, 9.7 ± 3.1, 13.4 ± 5.7, and 36.8 ± 10.0 μg/m3, respectively, in PM2.5 aerosols, for the above ions. The concentration of Na+, Mg2+, and Ca2+ were higher in spring and summer. The seasonal variation of secondary components NH4+, NO3-, and SO42- were similar; that means high concentration in winter and low concentration in fall. The results obtained from factor analysis suggested the presence of three main components/sources in the coarse and fine modes namely regional pollution, airborne road dust, and traffic emissions, which contributed 94.0% and 83.2% of the total variance of the system respectively for the PM2.5–10 and PM2.5 aerosols data set.