遵义PM_(2.5)中二次水溶性无机离子分布特征与来源

Distribution Characteristics and Sources of Secondary Watersoluble Inorganic Ions in PM_(2.5) in Zunyi City

2014年3-12月,对遵义丁字口(市区点)和凤凰山(背景点)按季节进行了PM_(2.5)的样品采集,对其中二次水溶性无机离子(NH_4^+、NO_3^-、SO_4^(2-))分布特征及存在形态进行研究。结果表明,NH_4^+、NO_3^-和SO_4^(2-)是遵义市PM_(2.5)的主要离子,其季节变化规律明显:NO_3^-、SO_4^(2-)的质量浓度表现为秋>冬>春>夏;NH_4^+则表现冬>秋>春>夏。丁字口PM_(2.5)中NH_4^+、NO_3^-和SO_4^(2-)的质量浓度均高于凤凰山。相关性分析表明,遵义PM_(2.5)中NH_4^+、NO_3^-、SO_4^(2-)在春、冬季主要以(NH_4)_2SO_4和NH_4NO_3的形式存在;夏季主要以NH_4HSO_4和NH_4NO_3的形式存在;秋季主要以NH_4HSO_4的形式存在。PM_(2.5)的酸碱度分析显示遵义PM_(2.5)主要呈酸性。SOR(硫表观氧化率)和NOR(氮表观氧化率)均值大于0.1,且丁字口SOR、NOR值略高于凤凰山;丁字口、凤凰山NO_3^-/SO_4^(2-)年均值分别为0.46±0.08和0.43±0.10,说明遵义市大气中的硫和氮主要来自于固定源。

PM2.5samples were simultaneously collected at Dingzikou（urban site） and Fenghuang Mountain（background site）by seasons from March 2014 to December 2014 in Zunyi City, Guizhou Province and the distribution characteristics and existing form of secondary water-soluble inorganic ions such as NH4^＋, NO3^-and SO4^2-in PM2.5were analyzed. The results showed that NH4^＋, NO3^-and SO4^2-were the major ions in PM2.5of the City and had obvious seasonal variation. The seasonal variation of mass concentrations of NO3^-and SO4^2-ranked as autumn winter spring summer, that of NH4^＋was winter autumnspringsummer. The mass concentrations of NH4^＋, NO3^-and SO4^2-in PM2.5of Dingzikou were higher than Fenghuang Mountain. The results of correlation analysis indicated that NH4^＋, NO3^-and SO4^2-probably existed in（NH4）2SO4, NH4NO3 in spring and winter, NH4HSO4 and NH4NO3in summer, and NH4HSO4 in autumn. The acidity of PM2.5samples showed that PM2.5was mainly acidic in the City. The average values of SOR（sulfur oxidation ratios） and NOR（ nitrogen oxidation ratios）were higher than 0.1, and the values of SOR and NOR of Dingzikou were slightly higher than Fenghuang Mountain, showing that sulfate and nitrate in PM2.5were mainly transformed by secondary reaction of SO2 and NOXin atmosphere. The average ratios of NO3^-and SO4^2-of Dingzikou and Fenghuang Mountain were 0.46±0.08, 0.43±0.10, respectively, indicating that sulfur and nitrogen in the atmosphere mainly came from stationary sources.