为了探讨西安市大气颗粒物在霾天气下水溶性离子的组分特征，2005年9月至2006年9月对西安大气TSP和PM2.5进行了观测研究。结果显示，西安大气TSP和PM2.5在霾天气的总水性离子浓度分别为135.0和72.4µg∙m-3。分析的11种阴阳离子(Na+、NH4+、K+、Mg2+、Ca2+、F-、Cl-、Br-、NO2-、NO3-和SO42-)中SO42-、NO3-、NH4+是TSP和PM2.5中的主要成分，这三种离子占总水溶性离子的百分比霾天气明显高于正常天气。pH测定的结果显示，霾天气大气颗粒物均比正常天气偏酸性。对比了不同天气下的SOR(SO2转化率)和NOR(NOX转化率)，发现霾天气SO2和NOX转化率高于正常天气，尤其是SO2在霾天气更易转化为SO42-。

In order to compare the water-soluble chemical species in ambient aerosol particles between haze days and normal days, TSP and PM2.5 samples were collected from Sep. 2005 to Sep. 2006. The result showed that the concentration of total water soluble ions in TSP and PM2.5 during haze days were 135.0 and 72.4 µg∙m-3, respectively. 11 water-soluble ions (Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, Br-, NO2-, NO3- and SO42-) were measured. The results showed that NH4+, SO42- and NO3- were major species both in haze and normal days, while the percentage of concentration of these three major ions in TSP and PM2.5 during haze days was higher than that in normal days. Measurements of pH values for aerosol particles dilute showed haze day samples was more acid than those in normal days. Calculated the oxidation ratio of sulfur (SOR) and nitrogen (NOR) in two kind of weather conditions, it revealed that ratio of transformation of SO2 and NOx in haze days were more higher than those in normal days, especially for SO2.