干旱区生态环境知识资源中心

Twenty-seven samples of typical loess and paleosol strata collected in nine different regions of the Chinese Loess Plateau (CLP) were fractionated into PM(1.0), PM(2.5), PM(10) and Total Suspended Particulates (TSP) (particulate matter with aerodynamic diameters less than 1.0, 2.5, 10 and 30 mu m, respectively) by a resuspension chamber at the Desert Research Institute (DRI; Reno, NV, United States). The amounts and isotope ratios of lead (Pb) were quantified in the loess samples. Our size-segregated analysis demonstrated that the Pb isotopic composition in the loess-paleosol deposits was preserved after grain-size sorting and that therefore the isotope ratio can serve as a proxy for source tracing. A similar pattern of Pb isotope ratios was observed for sediment collected from potential source regions and the loess samples suggested that the Gobi and deserts in southern Mongolia and northern China are major sources for the deposits in the CLP. No significant deviation of Pb isotope amount was found between the nine samples of loess and paleosol strata, implying the stability of loess sources during the glacial and interglacial regime.