苏州市PM2.5中水溶性离子的季节变化及来源分析

Seasonal Variation and Source Analysis of the Water-soluble Inorganic Ions in Fine Particulate Matter in Suzhou

2015年在苏州市城区采集大气细颗粒物PM_(2.5)样品共87套,用重量法分析了PM_(2.5)的质量浓度,离子色谱法分析了颗粒物中F-、Cl-、NO_3^-、SO_4^(2-)、Na^+、NH_4^+、K^+、Mg^(2+)和Ca^(2+),共9种水溶性无机离子.观测期间,苏州市PM_(2.5)的年均质量浓度为(74.26±38.01)μg·m-3,其季节特征为冬季>春季>秋季>夏季;9种水溶性离子的总质量浓度为(43.95±23.60)μg·m^(-3),各离子的浓度高低顺序为NO_3^->SO_4^(2-)>NH_4^+>Na^+>Cl^->K^+>Ca^(2+)>F->Mg^(2+);SNA(SO_4^(2-)、NO_3^-和NH_4^+三者的简称)是最主要的水溶性离子;SO_4^(2-)、NO_3^-和NH_4^+三者之间具有显著的相关性,它们在PM_(2.5)中主要是以NH_4NO_3和(NH_4)_2SO_4的结合方式存在.苏州市PM_(2.5)中水溶性离子的主要来源包括工业源、燃烧源、二次过程和建筑土壤尘等.

A total of 87 daily PM2.5 samples were eolleeted in the urban area of Suzhou city during 2015, representing spring, summer, autumn, winter, respectively. Mass concentration of PM2.5 was analyzed gravimetrieally. Water-soluble inorganic ions, including F^- , Cl^- , NO3^- , SO4^2- , Na ^＋ , NH4^＋ , K^ ＋ , Mg^2 ＋ and Ca^2 ＋ , were determined by ion ehromatography. The average mass eoncentration of PM2.5 was （74.26 ± 38.01 ） μg·m^-3. The seasonal variations of PM25 coneentrations deereased in the order of winter 〉 spring 〉 autumn 〉 summer. The average total mass concentrations of 9 ions was （43.95 ± 23.60） μg·m^-3, and the order of concentration of ions was NO3- 〉 SO4^2-- 〉 NH4 〉 Na ＋ 〉 Cl - 〉 K ＋ 〉 Ca^2 ＋ 〉 F - 〉 Mg^2 ＋ . Seasonal variation of ion concentrations was significant, with the highest eoncentration observed in winter and the lowest in summer. The seeondary inorganic speeies, including SO4^2-- , NO3- and NH4＋ （SNA） were the major eomponents of the water-soluble ions in PM2.5. SNA＇s eorrelations with each other were significant.SO4^2- , NO3- and NH4 were probably in the form of NH4NO3 and （NH4）2SO4. The [ NO3^-]/[ SO4^2- ] ratio approaehing to 1 implied that mobile sourees were as important as stationary sourees. Ion balance ealeulations indieated strong eorrelations between anion and cation equivalents. The PM2.5 was acidic. Industrial emission, combustion process, secondary formation and fugitive dust were the major sourees of the water-soluble ions in PM2.5.