Geochemistry of Trace and Rare Earth Elements in Red Soils from the Dongting Lake Area and Its Environmental Significance

Abstract

Trace element (TE) and rare earth element (REE) contents in red soils from the Dongting Lake area of China were determined to understanding the provenance and weathering characteristics of the red soils. The results showed similar REE distribution patterns among red soils from the Dongting Lake area, Xiashu loess from Zhenjiang, loess and Pliocene red soil from the Loess Plateau. These patterns implied a similar provenance from dust-storms, except for red soil R5 which formed by bedrock weathering and had significant light REE (LREE) enrichment and heavy REE (HREE) depletion due to longer weathering periods and higher intensity of weathering. Trace element, especially the Rb/Sr and Li/Ba ratios, and REE, especially the LREE/HREE ratio and δEu could trace weathering intensity. Higher Rb/Sr, Li/Ba, and LREE/HREE ratios and negative Eu anomalies were present in the red soils from the Dongting Lake area. The weathering intensity was in the decreasing order of R5 in the Dongting Lake area > red soils from the Dongting Lake area (including reticulate red soil, weak reticulate red soil, and homogeneous red soil formed by dust storms) > Xiashu loess from Zhenjiang > loess-paleosol and Pliocene red soil from the Loess Plateau. Variations in the TE and REE contents of soil could be effectively used to study the provenance and the weathering intensity.