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为研究国家大气背景点颗粒物质量浓度与水溶性离子组成特征，于2013年2月、7月、9月、12月分别对4个国家大气背景点进行了PM2．5及PM10的采样，通过超声萃取?IC法测定了样品中的9种水溶性离子（F－、Cl－、NO－3、SO2－4、Na＋、NH＋4、K＋、Mg2＋、Ca2＋）质量浓度，结果表明：（1）可吸入颗粒物浓度水平一、二季度重于三、四季度，PM2．5、PM10年均值分别为17μg·m－3、32μg·m－3，与其他主要国家和地区背景区域浓度相当，背景点大气状况良好；（2）PM2．5中水溶性离子比重全年波动不大，为35．5％—42．2％，浓度排序为SO2－4、NH＋4、NO－3＞ Ca2＋、Cl－、K＋、Na＋＞F－、Mg2＋，第一季度PM10中Ca2＋浓度显著升高，控制风沙尘将有效降低PM10的浓度；PM2．5及PM10中的9种水溶性离子在不同季节的浓度分布规律与颗粒物浓度类似，一季度较高，三、四季度较低；（3）二次离子是背景点区域的主要水溶性离子，浓度值与其他主要国家和地区相当．NO－3、SO2－4的物质的量浓度与NH＋4存在显著相关性，相关系数r为0．7539，斜率小于1，水溶性离子中酸性离子的量比铵根离子略占优势，对气溶胶酸度产生重要贡献．

To investigate the mass concentratation of fine particles and component characteristic of water?soluble ions in National Atmospheric Background, PM2.5 and PM10 samples were collected at 4 sites in four seasons of 2013. The mass concentrations of nine inorganic water?soluble ions were analyzed by ion chromatograph ( IC ) . The results show that the mass concentrations of inhalable particles were higher in the first season than those in the third and fourth seasons. The average annual value of PM2.5 and PM10 was 17μg·m-3 and 32μg·m-3, respectively, which are comparable to those in other major regions and countries. All of above results indicate that the atmospheric quality is good. Second, the contents of the water soluble ions wrer PM2.5 were between 35. 5%—42?2%. The concentration order of these ions is SO2-4 ,NH+4 ,NO-3>Ca2+,Cl-,K+,Na+>F-,Mg2+. The concentration of Ca2+in PM10 was higher in the first season, which indicates that controlling the dust concentration is of great importance to decrease the concentration of PM10. The concentration characteristic of the nine water soluble ions in PM2.5 and PM10 in different seasons is similar to that of fine particles, higher in the first season and lowers in the third and fourth seasons. Third, the secondary ions are the main water soluble ions in the background, whose concentrations are comparable to those in other major regions and countries. The concentrations of NO-3 and SO2-4 are obviously related to that of NH+4 , with the correlation coefficient ( r) of 0.754 and the slope less than 1, which shows the acidic ions are dominant in water soluable ions and affects a lot on the acidity of the aerosol.