Geochemical characteristics and environmental implications of loess sequences in the Loess Plateau

The major,trace,and rare earth elements of the Duanjiapo（DJP） section in the south of the Loess Plateau,the Jiaxian（JX） section in the north,and the Jiuzhoutai（JZT） section in the west are studied.The results show that the main elemental characteristics of loess in three profiles are consistent with the upper continental crust（UCC）.In terms of trace elements,Th,Nb,Zr,Hf,Y,Cs,W,Cr,V,Li,and Pb show relative enrichment compared with UCC;Rb,Ba,Sr and Be exhibit relative depletion.The average of ΣREE is 171.91 ppm with a negative anomaly for δEu and essentially no anomaly for δCe.The results of K2O/Na2O,Rb/Sr ratios,as well as the leaching coefficient from three profiles,indicate DJP> JX> JZT,suggesting that DJP experiences the strongest weathering leaching effect.The chemical index of alteration（CIA） reveals that all three profiles of loess are in the primary stage of Ca and Na depletion.DJP is generally in the early to moderate stage of chemical weathering,while JX and JZT are both in the early stage.