Ion chemistry and source identification of coarse and fine aerosols in an urban area of eastern central India

摘要

This work focuses on size segregated atmospheric aerosol mass concentrations and water soluble inorganic components in Chhattisgarh, the eastern central India. Investigation on the monitoring of ambient air levels of atmospheric particulates were done around a large source of primary anthropogenic paniculate emissions: the industrial area and coal based power plants. Chemical characterization was carried out for aerosol samples collected in urban area, Raipur, (21°14'N, 81°38'E) of Chhattisgarh region over a period of one year, using cascade impactor. Annual mean of mass concentration for coarse (PM_(2.5-10)) and fine (PM_(2.5)) aerosols were monitored to be 238.1 ±89.9 and 167.0± 75.3 μgm~(-3) respectively This work deals with the seasonal variation and meteorological influences of inorganic components of the aerosols viz. NO_3~-, Cl~- and SO_4~(2-), Mg~(2+), Na~+, K~+, Ca~(2+) and NH_4~+. The annual mean concentration of the inorganic components were monitored to be 3.8 ± 2.5,8.9 ± 2.7,10.2 ± 1.5,2.6 ± 0.6,8.7 ± 7.2, 4.6±1.8, 16.4±6.9 and 0.4±0.5μgm~(-3) respectively in coarse particles and 8.2±7.1, 6.8± 3.6, 46.5 ± 32.8, 1.7 ± 0.6, 7.4 ± 3.6, 5.9 ± 3.4, 10.2 ± 2.9, and 8.8 ± 7.7 μg m~(-3) respectively in fine particles, for the above ions. The average distribution of nitrate and sulphate in PM_(2.5-10) were found to be 1.6 and 4.2% and in PM_(2.5) were 4.9 and 27.9% respectively indicating the dominance of sulphate in both PM_(2.5-10) and PM_(2.5) particles. Here, industrial emission plays important role for contribution of PM_(2.5) particle loading in the atmosphere. The cation-anion rational analysis indicated that the PM_(2.5-10) particles were mostly neutralized and PM_(2.5) particle were acidic. The major ions were mainly in the form of NaCl>CaSO_4>K_2SO_4>MgSO_4>KCl> NH_4Cl>Ca(NO_3)_2>KNO_3>MgCl_2>Mg(NO_2)_2>NH_4NO_3>(NH_4)_2SO_4 in coarse aerosol particles and(NH_4)_2SO_4>K_2SO_4>CaSO_4>NaCl>NH_4NO_3>CaCl_2>KNO_3>MgCl_2>Ca(NO_3)_2>KCl>NH_4Cl in fine particles.