[Concentrations and Size Distributions of Water-soluble Inorganic Ions in Aerosol Particles in Taiyuan, Shanxi].

Size-resolved filter samples were collected in Taiyuan every other week from June 2012 to May 2014. The mass concentrations of water-soluble ions (Na, NH, K, Mg, Ca, F, Cl, NO and SO) were measured by ion chromatography. The results showed that the total concentrations of measured water-soluble ions were (15.39±9.91), (21.10±15.49) and (36.34±18.51) μg·m in PM, PM and PM, respectively. In PM and PM, secondary water-soluble ions (SO, NO and NH) comprised 87.59% and 86.30% of all water-soluble ions, respectively, while in PM, SO and Ca comprised 32.78% and 28.54% of all water-soluble ions, respectively. SO and NH had higher concentrations in winter and summer, and lower in spring and autumn. NO, Kand Cl presented similar seasonal variation with a descending order of winter >autumn >spring >summer, and Ca and Mg followed the sequence of spring >winter >autumn >summer. SO and NH showed a unimodal size distribution and the peak in the fine mode shifted from 0.43-0.65 μm in spring and autumn to 0.65-1.1 μm in summer. NO showed a bimodal size distribution. NO and NH were dominated by the fine mode peaking at 0.43-2.1 μm in winter, and NO was dominated by the coarse mode peaking at 4.7-5.8 μm in summer. K, Naand Cl also showed a bimodal size distribution with the fine mode at 0.43-1.1 μm and the coarse mode at 4.7-5.8 μm. Ca, Mg and F were unimodal with the peak in the coarse mode of 4.7-5.8 μm. On heavily polluted days, the mass concentrations of secondary water-soluble ions and Cl accumulated, and secondary water-soluble ions were unimodal with the peak in the fine mode of 1.1-2.1 μm. However, on clear days, secondary water-soluble ions showed a bimodal size distribution with the fine mode at 0.43-0.65 μm and the coarse mode at 4.7-5.8 μm. The peak of secondary water-soluble ions in the fine mode shifted. PCA analysis showed that the sources of water-soluble ions were dominated by the secondary formation, coal combustion, industrial emission, biomass burning, and soil particles or falling dust.