祁连山大雪山地区大气PM_(2.5)细粒子中可溶性离子特征

The Characteristics of Soluble Ions in PM_(2.5) Aerosol over the Qilian Shan Station of Glaciology and Ecologic Environment

为了研究祁连山大雪山地区大气PM2.5细粒子中可溶性无机离子组分的变化特征,于2010年7月至2011年7月在祁连山冰川与生态环境综合观测站附近采集46个大气PM2.5的Telfon滤膜样品,并应用离子色谱对可溶性离子进行了分析.结果显示:所测样品的阴、阳离子中,SO24-、NO3-、Ca2+和NH4+的质量浓度分别为1.54μg·m-3、0.38μg·m-3、0.73μg·m-3和0.22μg·m-3,累计约占到水溶性离子总量的88%.可溶性离子浓度呈现出春夏季节明显高于秋冬季节的特征,夏季的浓度最高,其次是春季、冬季和秋季.Cl-、Ca2+、Na+和Mg2+之间的相关性极高,SO24-和NO3-与大部分阳离子的相关性都很高,说明大部分硫酸盐是来自于中亚沙尘源区的自然源,而并非是通过人类活动造成的一次污染物通过二次反应过程得到的.NH4+仅与SO24-通过相关性检验说明,该地区NH3主要中和了大气中硫酸并生成(NH4)2SO4.该地区的大气环境主要来源于自然源的影响,但夏季风期间人为污染排放已经不可忽视,这也得到HYSPLIT后向轨迹模式的计算验证.

In order to explore the chemical characteristics and sources of PM2.5 aerosol ion components in the west Qilian Mountains,46 PM2.5 aerosol samples near the Qilian Shan Station of Glaciology and Ecologic Environment were collected form July 2010 to July 2011.The soluble inorganic ions were analyzed with Ion Chromatography.The results showed that SO2-4,NO-3,Ca2+ and NH+4 in the fine particles were the major components of cations and anions on the regional atmosphere.The soluble ion concentration was far lower than that in the sites affected by human activities seriously.It was close to the remote regional background atmospheric level,but it also had its own characteristics.The concentration showed significantly higher in spring and summer and lower in autumn and winter.The ratio of the ions in different seasons was not the same.The nature of regional atmospheric fine particles was exhibited alkaline by calculation of ion balance.Correlation analysis was used in this study to find out the major forms and the source of ions.There were high correlations between Cl-,Ca2+,Na+ and Mg2+.The correlations between SO2-4 and NO-3 and most of the cations were very high.It means part of sulfate coming from natural source of the sand and dust areas of Central Asia,rather than human activities.NH+4 passes the correlation testing only with SO2-4,indicated that NH3 is mainly neutralizes by sulfate.Atmospheric environment is mainly controlled by natural sources.However,during the summer monsoon,man-made pollution emission can not be ignored;it is also verified by the calculation of HYSPLIT trajectory model.