Concentration, speciation, and fractionation of rare earth elements in alluvial soils in contiguous karst landform, southwestern China

作者：Chunfang Dong, Zhixuan Han, Haotian Lu, Ruiwei Zhao, Yuqun Cai, Yang Li, Cheng Xu, Bimin Zhang · 发表于：Journal of Geochemical Exploration · 年份：2023 · DOI：10.1016/j.gexplo.2023.107360 · 被引用次数：14 · 研究领域：Geochemistry and Elemental Analysis、Geology and Paleoclimatology Research、Heavy metals in environment

Karst is a unique landform formed by strong chemical weathering of carbonate rocks . This study investigated the concentration and speciation of rare earth elements and yttrium (REY) in alluvial soils and REY fractionation from carbonate rocks and alluvial soils in the world's largest contiguous karst landform in southwestern China. The results showed that the REY of alluvial soils ranged from 73.77 to 1251.56 μg⋅g −1 , with a median value of 230.30 μg⋅g −1 , which was higher than that of alluvial soils across China (178 μg⋅g −1 ) and the upper continental crust (168 μg⋅g −1 ), revealing a high background of REY in these karst areas. Meanwhile, the average REY in alluvial soils (244.96 μg⋅g −1 ) was close to 14 times that in carbonate rocks (17.61 μg⋅g −1 ) in the study area, indicating that REY was significantly enriched in the pedogenesis . Correlation analysis showed that the REY concentration was not significantly related to any single factor (i.e., Fe 2 O 3 , MnO, Al 2 O 3 , TOC, pH, or CIX). BCR speciation analysis revealed a declining trend in the proportion of REY across the residual (F4, 73.21 %), reducible (F2, 19.40 %), oxidizable (F3, 6.89 %), and weakly acid-extracted (F1, 0.50 %) phases. Additionally, significant REY fractionations from carbonate rocks to alluvial soils were observed. The bedrock-normalized REY pattern revealed an enrichment of light rare-earth elements (LREE) and middle rare-earth elements (MREE), a depletion of heavy rare-earth elements and yt...