Chemical composition and source identification of submicron particles over Xi'an during winter

The objectives of this research were to characterize the chemical composition of submicron particles (PM_1.0) over Xi'an during winter and to identify their sources. Daily aerosol samples (PM_1.0) were collected continuously from Dec. 1st to Jan. 1st, 2006, and the concentrations of 11 water-soluble ions (Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, F^-, Cl^-, Br^-, NO₂⁺, NO₃^-, and SO₄^2-), and elemental carbon (EC) and organic carbon (OC) were determined in the filter samples. The mean PM_1.0 mass concentration was 149.7 μg m^-3. The total concentrations of 11 ions were 46% of PM_1.0mass concentration, indicating that water-soluble ions were the major components of submicron particles. The average OC and EC concentrations were 23.7±10.27 μg m^-3 and 4.6±1.8 μg m^-3, respectively. an important contributor to the regional carbonaceous aerosol. Factor analysis on the eight carbon fractions shows that 45.3% of total carbon in winter was attributed to coal combustion and gasoline automobile exhaust, 24.2% to diesel automobile exhaust, and 23.5% to biomass burning.