| Atmospheric particulate matter not only has an important impact on air quality and human health in urban areas, but also has a profound impact on climate change at the regional even global. The environmental effect of particles is largely determined by the physical and chemical properties, especially the particle size distribution, chemical composition, mixing state, particle acidity, moisture absorption and so on. The time resolution of tradition sampling method is poor, and the material is easy to be lost in the process of storage and transportation, which makes the inaccurate of the analysis result. Online mass spectrometry has a high temporal resolution, and it can effectively reduce the potential of human impact in off-line sampling and analysis. This research mainly uses the Single Particle Aerosol Mass Spectrometer (SPAMS) to study the atmospheric fine particulate matter in different seasons and different pollution process, besides the single particle composition characteristics, mixed states, sources and the aging process analysis of atmospheric fine particles in Beijing,2014. The main research contents of this paper include the following aspects:(1) The seasonal variation characteristics of the typical components of particulate matter in Beijing of 2014:Based on the characteristic ion method, this study statistics the hourly data of sulfate, nitrate and ammonium (SNA), size distribution and mixing condition characteristics were analysis. Combined with Concentration Weighted Trajectory Method, seasonal variation of SNA potential source areas distribution had been calculated. The results showed that the mixed state of sulfate, nitrate and ammonium in spring and summer was more stable than that in autumn and winter. The size distribution characteristics of sulfate and nitrate are very similar. The seasonal variation of SNA particle size distribution in the particle size distribution was:the maximum particle size segment of autumn particulate matter> summer> spring> winter. SNA potential source areas with similar spatial distribution characteristics, high potential source areas of SNA were mainly distributed in Beijing local and it’s southern regions, especially in Tianjin, Langfang, Hengshui, Baoding, Shijiazhuang and other places.In this study, ten types of metal particles (Pb, Cr, Mn, Cu, Zn, CD and Ti, as, V and Fe) were obtained by using characteristic ion method, the metal particle size were mainly distributed between 0.6-1.2μm. Heavy metal particles were mixed well with nitrate in the whole year, followed by sulfate, and less mixed with ammonium.(2) The characteristics of the chemical composition of particulate matter in the typical pollution episodes in Beijing,2014:In this study, we analyzed the main types of fine particulate matter in autumn (October) and winter (January) by SPAMS, and compared with the characteristics of autumn and winter, included particle types, the mixed state and so on. The results showed that in autumn and winter the particles contains the following types:dust particles (Dust), elemental carbon particles (EC), organic carbon particle matter (OC), elemental carbon and organic carbon hybrid particulate matter (ECOC), sodium and potassium particles (NAK), potassium rich particles (K), containing organic nitrogen (KCN) and heavy metal particles (Metal). In winter, the particle types were more complex than in autumn, besides the above eight types, also contain organic polymer (Macromolecular OC, MOC) and polycyclic aromatic hydrocarbon particles (PAHs); autumn particle size distribution mainly concentrated in between 0.5-0.8u m, During heavy pollution episodes, EC, K and OC were the main particle types. Regardless of pollution or cleaning episodes, nitrate and sulfate were occupied a large proportion in all kinds of particles in autumn, which was different in winter, ammonium accounted for ratio also has an obvious increase, especially in EC and K particles. In addition, except for nitrate and sulfate, ammonium also plays the vital role in pollution episodes during autumn. Winter particle size distribution mainly concentrated between 0.5-0.6μm, during the heavy pollution episodes, OC, MOC and PAHs were the main particle types, sulfate and nitrate were more likely mixed with carbonaceous particles; In this study, we selected a shorten but strong dust episode during 17:00 to 22:00 in April 15,2014, the variation characteristics of the particulate matter in four hours before, during and after the dust storm were analyzed. The results showed that OC and K were the main particle types before dust storm. Dust particles were the main component during dust storm, in which Dust_Fe (Dust particles containing element Fe), Dust_Ca (Dust particles containing element Ca), and Dust_Si (Dust particles containing element Si) accounted for the major proportion. EC particles accounted for the largest proportion after dust storm. During dust storm, the number of Dust_Fe, Dust_Ca and Dust_Si increased most obviously, which were mixed well with nitrate. On the contrary, the number of Dust_Al (Dust particles containing element Al) and Dust_metal (Dust particles containing heavy metals) did not change significantly, which were mixed well with sulfate. That showed the important role of nitrate in the dust storm episode. |
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