Distribution of Trace Elements in Holocene Loess-paleosol Sequence and Environmental Change in Lower Reaches of The Yellow River

Abstract

Based on field investigation, samples in loess-paleosol sequence profile were collected systematically at Longshan site in Shangdong province in lower reaches of The Yellow River. Trace elements(Mn, Cu, Ba, Ni, Pb, Rb, Sr, Ti, V and Zn) were measured and analyzed systematically by X-Ray and compared with climate substitution index(grain size, Rb/Sr, Ba/Sr). The results as follows:(1) According to the significant correlation between the content of Ti, Ba, Cu, Ni, V, Zn, Rb, Pb, Sr in the LS loess-soil sequence and the index of soil strength (soil grain size, Rb/Sr, Ba/Sr), it can be concluded that the migration and change of trace elements in Holocene period were mainly affected by the environmental evolution of this period. Mn is insensitive to climate change in this profile. The content of Pb in the surface layer of soil is the highest, which may be caused by human activities. (2) The contents of Ti, Ba, Cu, Ni, V, Zn and Rb in the paleosol( S0 ) were accumulated accompanied by the clay(< 5μm) increase while the coarse silt(10∼50μm) reduced, suggesting the intensified pedogenic modification to the accumulated dust when it was humid climate. It implied that the climate was warm and humid during the mid-Holocene optimum. (3) Content of Ti, Ba, Cu, Ni, V, Zn, Rb and clay(< 5μm)in loess layer (Lt, L1, L0) was lower and coarse silt (10-50μm) content was higher when compared with the paleosol layer (S0), suggesting that the intensity of soil formation was weak and aeolian sand activity was frequent. It further indicated that the paleoenvironment was cold and dry with frequent dust storms during the periods of loess formation.