The objective of this study was to characterize the mass concentration and chemical composition of aerosol particles（PM2.5） collected at Tongliao（Inner Mongolia Autonomous Region, China）, a site in Horqin Sand-land in northeast China. During spring 2005, the mass concentration for PM2.5 was （126±71）μg/m^3 in average. Five dust storm events were monitored with higher concentration of （255 ± 77）μg/m^3 in average than the non dusty days of （106 ± 44）μg/m^3. Concentrations for 20 elements were obtained by the PIXE method. Mass concentrations of ALl, Mg, Si, K, Ca, Ti, Mn, and V, which increased with the PM2.5 concentration, were higher than the pollution elements （S, Cl, Zn, Ar, Se, Br, and Pb）. Enrichment factor relative to crust material was also calculated, which showed dust trace elements were mainly from earth upper crust and pollution elements were dominated the anthropogenic aerosols. The Si/Al, Ca/Al, and Fe/Al ratios in PM2.5 samples at Tongliao were 4.07, 0.94, and 0.82, respectively, which were remarkably different with those on other source regions, such as ＂Western desert source region＂, ＂North desert source region＂ and central Asia source. Air mass back-trajectory analysis identified three kinds of general pathways were associated with the aerosol particle transport to Tongliao, but have the similar elemental ratios, implying that elemental signatures for dust aerosol from Horqin Sand-land were different with other regions.
Measurements were performed in spring 2001 and 2002 to determine the characteristics of soil dust in the Chinese desert region of Dunhuang, one of the ground sites of the Asia-Pacific Regional Aerosol Characterization Experiment （ACE-Asia）. The mean mass concentrations of total suspended particle matter during the spring of 2001 and 2002 were 317μg m^-3 and 307μg m^-3, respectively. Eleven dust storm events were observed with a mean aerosol concentration of 1095μg m^-3, while the non-dusty days with calm or weak wind speed had a background aerosol loading of 196μg m^-3 on average in the springtime. The main minerals detected in the aerosol samples by X-ray diffraction were illite, kaolinite, chlorite, quartz, feldspar, calcite and dolomite. Gypsum, halite and amphibole were also detected in a few samples. The mineralogical data also show that Asian dust is characterized by a kaolinite to chlorite （K/C） ratio lower than 1 whereas Saharan dust exhibits a K/C ratio larger than 2. Air mass back-trajectory analysis show that three families of pathways are associated with the aerosol particle transport to Dunhuang, but these have similar K/C ratios, which further demonstrates that the mineralogical characteristics of Asian dust are different from African dust.
