Stable sulfur isotope ratios and water-soluble inorganic compositions of PM10 in Yichang City, central China.

Chemical and sulfate-sulfur isotopic compositions of water-soluble inorganic ions were analyzed for aerosol sample particulate matter with aerodynamic diameter ≤10 μm (PM10) collected during 17-28 December 2012 at Yichang City, Hubei Province, central China. Most water-soluble inorganic ions, except for NO3 (-) and NH4 (+), showed slightly higher concentration in daytime than in nighttime, and the major detected ions followed the order of SO4 (2-) > NO3 (-) > Ca(2+) > Na(+) > NH4 (+) > Cl(-) in daytime and nighttime, of which SO4 (2-) is the most abundant ionic component that accounted for about 49.1 and 49.3 % of the total mass of analyzed ions in daytime and nighttime, respectively. According to the correlation coefficients among the mass concentrations of water-soluble inorganic ions, there may mainly exist in forms of (NH4)2SO4 and NH4NO3 in daytime and NH4NO3 in nighttime. The δ(34)S values of sulfate ranged from +2.82 to +4.63 ‰ (average +3.97 ‰) in daytime and from +2.90 to +5.39 ‰ (average +4.08 ‰) in nighttime, indicating that the source of sulfate in PM10 was mainly derived from coal burning (δ(34)S, +3.68 ‰) in Yichang City. The [NO3 (-)]/[SO4 (2-)] mass ratio varied between 0.2 and 0.6 with an average of 0.4 in daytime and 0.1 to 0.8 with an average of 0.4 in nighttime, which implying that the stationary source emissions would be more important than the vehicle emissions in the studied area. As a whole, the mixture of coal burning, vehicle exhaust, and resuspended road dust would be responsible for the sources of PM10 in Yichang City during wintertime.