2007年北京夏季降水分段采样酸度和化学成分分析  

Variation of pH and Chemical Composition of Precipitation by Multi-step Sampling in Summer of Beijing 2007

作　　者：王跃思[1] 李雪[1] 姚利[1] 赵亚南[1] 潘月鹏[1] 

机构地区：[1]中国科学院大气物理研究所,北京100029

出　　处：《环境科学》2009年第9期2715-2721,共7页Environmental Science

基　　金：国家重点基础研究发展规划(973)项目(2007CB407303);中国科学院知识创新工程重大研究项目(KZCX1-YW-06-01);国家杰出青年科学基金项目(40525016)

摘　　要：为掌握降水酸度和污染性化学成分随降水持续时间的变化规律,对北京2007年夏季5次典型降水过程分时段采样,分别测定了pH值、电导率,并分析了其中水溶性大气污染成分SO4^2-、NO3^-、NH4^＋等随时间的变化特征.结果表明,pH加权平均值在降水初期为5.70±0.73,为非酸雨;平缓期为4.35±0.56,呈酸雨特征.pH、电导率和各离子浓度随降水时间的持续而迅速下降,10-45 min后进入平缓期,各污染离子随之下降率为50%～90%.来自北京西北方向云团的降水（8月1日）pH值较高、污染物浓度较低,SO4^2-、NO3^-和NH4^＋分别为65.4、23.9和117.3μeq/L;而来自偏南云团降水（8月6日）pH值较低、污染物浓度较高,SO4^2-、NO3^-和NH4＋浓度分别为310.8、95.7和249.8μeq/L.北京夏季二次粒子浓度升高,将使降水酸化加剧.In order to understand variations of pH and chemical composition of precipitation in Beijing, 5 precipitation events in summer time of 2007 were sampled step by step sequentially on time, and the variations of pH, EC and the characterization of water-soluble ion such as NH4^＋ , SO4^2- and NO3^- were analyzed. The results showed that pH was 5.70 ± 0.73 in the beginning （before-35 min） and the precipitation was not acidic, but in the steady period （after-35 min） pH was 4.35 ±0.56 and the raining water presented acidity actually. Simultaneously, pH, EC and concentration of ions decreased rapidly with the raining continuously, 10-45 min later that became nearly constant and the concentration of water soluble ions decreased 50%-90% compare to beginning. The major pollutants in the precipitation on Aug. 1, which the raining air mass came from the northwest, was low and the concentrations of NH4 , SO4^2- and NOr were 65.4, 23.9 and 117.3 μeq/L, respectively; while the major pollutants in the precipitation on Aug. 6, which the air mass came from south, was high and the concentrations of NH4^＋, SO4^＋ and NO4^2- were 310.8, 95.7 and 249.8μeq/L. But acidic precipitation was much higher when the air mass came from south than from northwest. The increasing fine particles from photo-chemical reaction in summer time of Beijing will result that the precipitation of the rain will be more and more acidic.

关 键 词：降水 分段采样 PH 污染离子 后向轨迹 

分 类 号：X517[环境科学与工程—环境工程]