Effects of in situ leaching on the origin and migration of rare earth elements in aqueous systems of South China: Insights based on REE patterns, and Ce and Eu anomalies

• Published in: Journal of hazardous materials 2022-08, Vol.435, p.128959-128959, Article 128959
• Main Authors: Liu, Xiao-Rui, Liu, Wen-Shen, Tang, Ye-Tao, Wang, Shi-Zhong, Cao, Ying-Jie, Chen, Zi-Wu, Xie, Can-Die, Liu, Chang, Guo, Mei-Na, Qiu, Rong-Liang
• Format: Article
• Language: English
• Subjects: China; Environmental Monitoring - methods; Eu anomaly; Groundwater; Ion-adsorption REE mine; Metals, Rare Earth; Mining; REE colloid; REE fractionation; Soil; Water
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2022.128959

In situ leaching of ion-adsorption rare earth element (REE) deposits has released large amounts of REE-containing wastewater. However, the origin, speciation, distribution and migration of REEs in aqueous systems of the mining catchment are poorly understood. Groundwater, surface water, in situ leachates and weathered granite soil samples were collected from a catchment affected by mining activities in South China. The REE concentrations in groundwater (6.18 × 10–3–0.49 μmol L–1) and surface water (2.54–44.05 μmol L–1) decreased from upstream to downstream. REEs in groundwater were detected in organic matter associated (FA-REE) colloids, while the REE3+ and REE(SO4)+ were converted to REE(CO3)+ and FA-REE colloids from leachates and upstream surface water to downstream. The REE patterns of leachates and upstream groundwater (light and middle REE enrichment) resembled those of soil, but showed heavy REE enrichment due to FA-REE colloids in the downstream. REE in surface water were derived from middle REE enriched leachate. The Ce and Eu anomalies in the water samples indicated the REE origin (i.e., mining activities) and the hydrological variations (e.g., oxidation environment and water-rock interaction). Our results reveal the origin and fate of REE in aqueous systems of ion-adsorption REE mining catchments. [Display omitted] •REE concentration in groundwater is lower than in surface water.•REE speciation differs in groundwater and surface water.•REE pattern in leachate and groundwater upstream reflects the parent rock pattern.•Organic matter-associated colloids dominate the REE pattern of groundwater.•Ce and Eu anomalies indicate REE origin and hydrological variations.