Study On The Characteristics Of Mass Concentration And Inorganic Components And The Sources Of Aerosol In Beijing And Its Surrounding Area

The concentrations of PM10 keep high value and PM10 is the primary pollution matter of atmospheric complex pollution in many cities in China. The water soluble ions and metal elements are the key compositions of the aerosol, whose distribution characteristics of mass concentrations in different sizes indicate the sources and the formation of secondary particles, and are used to study the concentrations of primary particles and their chemical characteristics. The results of the study are the elementary foundation about the influence of aerosol particle on climate and environment change and the harm of the fine particle to the human health.The concentrations of PM2.5 and PM10 were observed by the ambient particle monitor (RP1400a) in Beijing and Xianghe in Hebei province from March to August, 2004; at different height of 325m meteorological tower in Beijing from October, 2004 to December, 2006; in Beijing, Tianjin and Xinglong regional background station August to December, 2006. Aerosol samples were simultaneously collected by Andersen cascade sampler at the height of 8m, 80m and 240m of 325m meteorological tower in Beijing during September, 2004. The same experiment was carried at 10m, 120m, and 220m of 255m meteorological tower in Tianjin from August to September, 2006. Aerosol samples were collected with Andersen cascade sampler at the summit of mount Tai in Shandong province during June 2006. The water soluble ionic concentrations were analyzed by Ion Chromatogram (IC, Dionex ICS-90) and the metal elements were analyzed by Inductively Coupled Plasma-Mass Spectrometer (ICP-MS, Agilent 7500a).The concentration of PM10 in Beijing is 1.6 times more than the one of regional background. The annual average concentrations of PM10 in Beijing are 151, 144 and 162μg·m-3, which exceed 44~62% of national standard. The annual average ratios of PM2.5 to PM10 are 46.3%, 49.6%, 50.5%, and the high value appears in summer when the atmospheric photochemistry is strong. The combustion of fossil fuel in winter and stable weather process in autumn also lead to the high value of the ratio. The characteristics of diurnal variation of PM10 in urban area are different from it in background region. Diurnal variation of major air pollutants in urban area were mainly affected by human activity, while the processes of atmospheric physics were the major drive of diurnal variation for air pollutants in background region. Atmospheric aerosol mass concentrations have uniform distributions from 8m to 80m in Beijing, while those of 240m have vertical variation with the lower, especially during night. PM2.5 and PM10 concentrations are 15% and 29% lower than the layer below 100m. The factors that impact on the vertical distributions of the atmospheric aerosol mass concentrations are strong inversion layer, wind speed and wind direction.It shows that there are three types size distribution:①ions whose mass resided mainly within the accumulation mode with the peak at 0.43~1.1μm(SO42-, NH4+,NO3-,K+),②ions whose mass resided mainly within coarse particles with the peak at 4.7~5.8μm(Ca2+,Mg2+),③ions which were two modes with the peak at 0.65~1.1μm and 4.7~5.8μm(NO3-,Cl-). The mass median diameter of SO42- with high concentration is between 0.5μm and 0.8μm, and belongs to the"drop mode". The concentration of ions such as SO42-, NO3-, NH4+ and K+ has a huge variety and the ions(SO42-, NO3-, NH4+) reach the high value when the humid air mass come from the south.The metal elemental concentrations of aerosol were analyzed by ICP/MS. It shows that there are four types size distribution:①metals whose mass resided mainly within coarse particles with the peak at 3.3~5.8μm included Ca, Fe, Al, Mg, Ba, Sr and Zr.②metals whose mass resided mainly within the accumulation mode with the peak at 0.65~1.1μm included K, Pb, As, Cd.③metals whose mass resided mainly within the two modes with the peaks at 0.65~1.1μm and 3.3~5.8μm included Zn, Sn, Cu, Ni. metals④which were distributed between fine, intermediate and coarse modes included Na, Cr, Mn and V. The elements with the coarse mode have the concentration peak at 80m and the elements with the fine mode have uniformly vertical distribution. Furthermore, concentrations of crustal elements go up when the air mass come from the north and concentrations of pollution elements raise when the air mass come from the south at the summit of Mount Tai.