Hydrogeochemical and health implications of rare earth elements in groundwater: A review

Abstract

Rare earth elements (REEs) are increasingly accumulated in groundwater due to anthropogenic activities, but their fate, hydrogeochemical behavior, and health impacts remain poorly understood and regulated. We have systematically reviewed the scientific literature over the last decades concerning sources, geochemical processes, potential tracer, and health impacts of REEs in groundwaters. REEs in groundwaters are mainly sourced from bedrock and occasionally from anthropogenic activities. Geochemical processes, including redox processes, complexation, adsorption, and desorption, modify REE signatures in groundwater. Redox conditions can change the redox state of Ce and result in anomalies, which can reflect redox processes in groundwater systems. We systematically concluded that REE concentrations and patterns can be used to delineate sources and geochemical processes of geogenic redox-sensitive elements in groundwater (such as arsenic and uranium). Anthropogenic REEs from wastewater, fertilizer, mining, and solid waste can be introduced into groundwater systems, which disturbs the natural REE signatures. We disentangled that delineating groundwater contamination and tracing related geochemical processes can be beneficial from differentiating geogenic REE signatures from anthropogenic REE disturbance. Long-term consumption of low-dose REE-bearing drinking water is suggested to cause diverse significant damage to human health. Novel investigations are required to perform on pathways of REE intake, potential mitigation measures, and drinking water guidelines for REE concentrations to minimize their health impacts. Future studies are needed to better understand environmental behavior and epidemiological impacts of anthropogenic REEs in groundwaters.