In recent years, the Asian dust storms occurred frequently. It was estimated that approximately eight hundred million metric tons of Asian dusts transported to the atmosphere yearly. During the dust storm period, Asian dusts not only induce poor air quality, but also reduce atmospheric visibility and influence human health. In order to investigate the physicochemical characteristics and source allocation of Asian dusts, this study collect the Asian dusts in the Pescadores Islands during the years of 2002~2006. In addition, this study collected top soils in three regions of Inner Mongolia and resuspended the soil samples in a resuspension chamber to analyze their chemical composition. Moreover, this study applied enrichment factor analysis (EF) and grey relational analysis to allocate the potential sources of Asian dusts and compare them with the transportation routes obtained from backward trajectory. During Asian dust storm periods, the concentration of atmospheric particulate matter (PM10) in the Pescadores Islands increased significantly, probably is 3~6 times of PM10 during non-dust storm periods. Among them, coarse particles (PM2.5-10) particularly rose from 10~30 £gg/m3 to 80~130 £gg/m3 and the size distribution changed from bi-modal distribution to single modal distribution of coarse particles during Asian dust storm periods. This study further analyzed the chemical composition of Asian dusts, including water-soluble ionic species, carbon contents, and metallic contents. For fine particles (PM2.5), the order of water-soluble ionic species was SO42- > NH4+ > NO3- > Cl- > Ca2+ > Na+ > K+ > Mg2+ > F-. For coarse particles (PM2.5-10), the order of water-soluble ionic species was Cl- > SO42- > NO3- > Na+ > Ca2+ > NH4+ > Mg2+ > K+ > F-. The carbon contents distributes mainly in fine particles. The major contents of both fine and coarse particles were crustal elements (i.e. Al, Fe, Na, Mg, K, Ca, and Sr). In addition to the analysis of physicochemical characteristics of Asian dusts, this study applied HYSPLIT MODEL to figure out their transportation routes by backward trajectory. According to the backward trajectories, this study compartmentalized Asian dusts storm transportation routes into three categories: Eastward Transportation and Retraced (ETR), Southeasterly Transportation and Circumrotated (STC), and Straight Southeasterly Transportation (SST). Analyzing the spatial and temporary background variables to investigate the influence of transportation routes on Asian dusts¡¦ physicochemical characteristic. This study revealed that the physicochemical characteristics were very similar for same category of Asian dust storms, which can be used to allocate the source regions of Asian dust storms. This study resuspended the soil samples collected in Inner Mongolia inside a resuspension chamber and collected the suspended particles (PM2.5, PM2.5-10) for chemical analysis. Chemical analysis results indicated that the fingerprints of chemical composition for different regions were similar but still distinguishable, which can be used to identify the source areas of Asian dusts. This study further compare and correlate the Asian dusts collected at the Pescadores Islands during Asian dust storm periods with the soils collected in Inner Mongolia chemically by enrichment factor and grey relational analysis. This study further compared the source allocation of Asian dust storms obtained from enrichment factor, grey relational analysis, and backward trajectory and found the results of these three methods were quite similar. For enrichment factor analysis, 88% of similarity was obtained by using two separate reference elements (Al and Fe). The similarity of backward trajectory and grey relational analysis reached as high as 83%. Moreover, the backward trajectory and enrichment factor were similar up to 75%, while the grey relational analysis and enrichment factor were similar up to 69%. Overall, two out of three aforementioned methods can effectively allocate the source regions of Asian dusts by 94%, while all three methods can successfully allocate the source regions of Asian dusts by 56%. Comparison of three aforementioned methods showed that they can be applied to allocate the source regions of Asian dusts.

ABSTRACT In this study, we conducted an intensive sampling of Asian dusts at Pescadores Islands for heavy Asian continental sandstorms (ACS) from February 22 to March 6, 2008. To investigate the succession of anthropogenic and natural pollutants for the ACS transportation, PM2.5 and PM2.5-10 were sampled by two dichotomous samplers once every four hours during the ACS periods, and furthermore analyzed their physicochemical properties, including mass concentrations, particle size distribution, water-soluble ionic species, carbonaceous contents, and metallic contents. Experimental results indicated that it was mainly fine particles (PM2.5) prior to the ACS, and the percentage of anthropogenic species (i.e., SO42-, NH4+, NO3-, Zn, Mn and OC) increased dramatically. However, it changed to coarse particles while the ACS overwhelming, and the percentage of crustal/marine species (i.e., Cl-, Na+, Ca2+, Mg2+, Ca, Al, Mg and EC) increased. After the ACS, the concentrations of all species decreased substantially. However, the percentage of Cl- and Na+ increased, suggesting that sea breeze has constant influences on local suspended particles. In addition to the analysis of physicochemical properties of Asian dusts, this study applied a HYSPLIT MODEL to figure out the transportation routes and the source regions of the ACS. Backward trajectory analysis showed that the ACS was originated from the east portion of Inner Mongolia, namely the Onqin Daga Sandy Land and the Horqin Sandy Land. Moreover, seventeen soil samples were collected from the Tengger Desert, the Mu Us Desert, the Onqin Daga Sandy Land, and the Horqin Sandy Land in Inner Mongolia during the year of 2005. The soil samples were resuspended in a resuspension chamber and then collected by a dichotomous sampler. This study focused on PM2.5-10 particles that mainly influence the downwind regions, and then took the ACS samples and the resuspended soil samples to measure the Sr isotopic characteristics of 87Sr/86Sr ratios by a multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). To characterize the isotopic properties of resuspended dust particles from the ACS source regions in northern China, and to correlate Asian dusts at the downwind regions of ACS with the source regions by Duncan¡¦s Multiple Range Test (DMR). The DMR results showed that the ACS was probably originated from the east portion of Inner Mongolia, namely the Onqin Daga Sandy Land and the Horqin Sandy Land, which concurred with the backward trajectory analysis.

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