The Distributed Characteristics Of Water Soluable Sulfate And Nitrate In Atmospheric Particles In Beijing

Sulfate and nitrate are the important compositions of inhalerable particulate matter. The source of sulfate and nitrate can be divide into the primary source and secondary source from which the sulfate and nitrate are generated by Atmospheric chemical reactions in the atmosphere. The sulfate and the nitrate as the representatives of secondary sources are brought to people's attention gradually in the controlling of Beijing inhalerable particulate matter contamination in Beijing.The mass concentration in different particle diameters and the distribution of sulfate and nitrate can indicate that there originations and formation mechanisms. In this study,the particle matter samples of atmosphere environment in Beijing were sampled by Micro-Orifice Uniform Deposit Impactor (MOUDI) to separate the particle matter which particulate size is smaller than 10μm according to the ten different diameter ranges,between May 2008 and April 2009.And the concentration of SO42-,NO3-,NH4+ and other ions were detected by using ion chromatograph technology.There were several important findings in this dissertation. Firstly,the mass concentration of water-soluble ions of PM10 and PM2.5 in Beijing are 39.8±14.7μg/m3 and 33.3±12.6μg/m3 respectively,accounted for 36.6±4.6% and of total mass of PM10 and 43.4±5.7% for the case of PM2.5. SO42-,NO3-,NH4+ are the important components of water-soluble ions. They accounted for 67.3% of water-soluble ions in PM10 total,and 75.2% for the case of PM2.5. Secondly,the mass size distributions of SO42-,NO3-,NH4+ were mostly showed with single mode with peak at the diameter range of 0.32~0.56μm. When the environment humidity increases,the mass size distributions of SO42-,NO3-,NH4+ present in fine mode with peak at 0.56~1.0μm or 1.0~1.8μm. Thirdly,SO42-,NO3-,NH4+ mainly existed with the forms of (NH4)2SO4 and NH4NO3. A small percentage of NO3- exist in NaNO3,KNO3 and the Ca(NO3)2. Moreover,NH4+ can also form NH4Cl in a small quantity. Therefore,the mass concentrations of (NH4)2SO4,NH4NO3 and NH4Cl in PM10 which are computed using the concentration of NH4+ in each stage into account with ionic equilibrium are 17.0±8.2μg/m3,8.8±3.3μg/m3 and 0.8±0.4μg/m3 respectively. The sum of the three accounts for 23.2±4.3% of PM10 . Lastly,humidity is a remarkable climate factor which can affect the mass concentration of SO42-,NO3-,NH4+. When the humidity increases,the peaks of the mass size distributions of SO42-,NO3-,NH4+ present at"droplet mode",which indicates that the clouds reaction is the important way of sulfate and nitrate formation.