[Distribution Characteristics of Water-soluble Ions in Size-segregated Particulate Matters in Taiyuan].

The distributions of size-segregated particles (PM ₁₀ ) and water-soluble ions (WSIs) in Taiyuan were studied from July 2014 to April 2015 by TE-235 aerosol sampling and ion chromatography analyzing. As the results shown, the daily PM ₁₀ level was 173.7 μg·m ^-3 , which exceeded the Grade Ⅱ limitation value in the Ambient Air Quality Standard (150 μg·m ^-3 , GB 3095-2012). PM ₁₀ levels varied seasonally, and its were 199.1 and 194.2 μg·m ^-3 in winter and spring, respectively, which were much higher than those in summer. The PM ₁₀ size-segregated was bimodal distribution for the range of 0-0.95 and 3.0-7.2 μm. The concentration of WSIs was the highest in winter, followed by summer and spring. SO ₄ ^2- , NO ₃ ^- and NH ₄ ⁺ were the main water soluble ions and accounted for 66% to 80% of the total WSIs. SO ₄ ^2- , K ⁺ , NH ₄ ⁺ and Cl ^- showed a unimodal distribution at <0.95 μm in all samples, while Ca ²⁺ and Mg ²⁺ showed a bimodal distribution at <0.95 μm and 3.0-7.2 μm. NO ₃ ^- showed a unimodal size distribution at <0.95 μm in winter and spring, compared with a bimodal distribution at <0.95 μm and 3.0-7.2 μm in summer. By the correlation analysis, PM ₁₀ and WSIs decreased with the increase of wind speed in summer and winter other than in spring for the road-dust re-suspension by strong wind. Based on the ratio analysis of NO ₃ ^- /SO ₄ ^2- and Mg ²⁺ /Ca ²⁺ , coal combustion was the main source of NO ₃ ^- and SO ₄ ^2- , while Mg ²⁺ and Ca ²⁺ were mainly from the dust and coal combustion.