Geochemistry and environmental effects of rare-earth elements in laterites from Yunnan province, SW China

Abstract

Rare-earth elements (REEs) in soils are influenced by pedogenic processes and anthropogenic activities. To interpret the fractionation and migration of REEs during weathering in (sub-)tropical regions, the distribution, fractionation patterns and environmental effects of REEs in laterites were investigated in this study. Soil samples from two laterite profiles (labelled S1 and S2) were collected and the concentrations of REEs were measured with an inductively coupled plasma mass spectrometer. The results suggest that the ΣREEs of S2 (119 ± 10 mg kg–1 to 209 ± 10 mg kg–1) have a higher concentration and a wider variation than those of S1 (114 ± 5 mg kg–1 to 154 ± 8 mg kg–1). The REEs in both laterite profiles are enriched in the order HREEs > LREEs > MREEs. The distribution patterns of laterite profiles show evidence of inheritance from parent granites. The laterites preferentially incorporated HREEs, and secondary Fe2O3 and clay minerals were likely to affect the fractionation of REEs in laterites. The enrichment factor of REEs varied from 11.1 to 18.9 for S1 and 10.0 to 27.6 for S1, indicating potential pollution by REEs. The accumulation of REEs in laterites by mining activity should be a concern of government environmental agencies. Supplementary material: Table S1, Reference values of REEs and Fe2O3 in standard materials (GSS-18 and GSS-20); Table S2, Measurement parameters of ICP-MS; Table S3, Concentrations of REEs and Fe2O3 in laterite profiles from Yunnan province, SW China; Table S4, The enrichment factor for the laterite profiles from Yunnan province, SW China are available at https://doi.org/10.6084/m9.figshare.c.5609234