Geochemical Behavior of Rare Earth Elements and Their Use as Environmental Indicators

Rare earth elements (REEs) are increasingly being used in cutting-edge technologies, such as electric vehicles, wind turbines, and high-performance electronics, raising concerns over their environment accumulation and ecotoxicity.However, integrated reviews on their geochemical behavior and environmental occurrence remain limited.Geochemical proxies-including cerium (Ce) and europium (Eu) anomalies, light-to-heavy REE ratios (LREE/HREE), and normalized REE distribution patternsoffer potential as metrics for investigating source attribution, particularly for advanced industrial contamination where conventional heavy metal indicators are insufficient.Recently, the incorporation of REEs into positive matrix factorization models has emerged as a new strategy for precisely quantifying source contributions from both traditional and advanced industries.In this article, the geochemical behavior of REEs and their speciation in soils and sediments, fractionation via the sequential extraction method, and applicability as environmental indicators are systematically reviewed, thereby providing a reference framework for advancing REE-based environmental geochemical investigations.