title: [Variation of pH and chemical composition of precipitation by multi-step sampling in summer of Beijing 2007].
abstract: 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 NO3- were 65.4, 23.9 and 117.3 microeq/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(2-) and NO3- were 310.8, 95.7 and 249.8 microeq/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.
authors.affiliation: Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. wys@mail.iap.ac.cn
authors.forename: Yue-Si
authors.initials: YS
authors.lastname: Wang
authors.forename: Xue
authors.initials: X
authors.lastname: Li
authors.forename: Li
authors.initials: L
authors.lastname: Yao
authors.forename: Ya-Nan
authors.initials: YN
authors.lastname: Zhao
authors.forename: Yue-Peng
authors.initials: YP
authors.lastname: Pan
mesh_terms: D015258:Acid Rain / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis*; D002681:China; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000032:analysis*; D000644:Quaternary Ammonium Compounds / Q000032:analysis*; D011891:Rain / Q000737:chemistry*; D012621:Seasons; D013458:Sulfur Dioxide / Q000032:analysis*
chemical_list: D015258:Acid Rain; D000393:Air Pollutants; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D013458:Sulfur Dioxide