Iron-organic matter colloid control rare earth element environmental mobility

Rare earth elements (REE) have raised significant environmental concerns due to their increasing use in human activities and subsequent release into the environment. Hence, in the context of growing demand for "green" technologies and potential mismanagement of their life cycle, understanding their potential mobility within and between environmental compartments becomes crucial for evaluating their environmental risks. Colloids emerge as primary carriers/vectors facilitating REE mobility and transfer in the environment. This work addresses major topics related to the control exerted by colloids on the REE speciation and subsequent patterns. Among colloids, iron-organic matter colloids have been identified as the major REE carrier in surface water under various pedoclimatic conditions. Compelling evidences were provided that the mixing of iron-, organic- and iron-organic colloids could explain both REE concentration and pattern under environmental conditions. However, there is currently a lack of data on the specific distribution of REE between the iron and organic matter phases within Fe-OM colloids. It remains unclear whether REE distribution is primarily controlled by colloid mixing since structural rearrangements of Fe-OM colloids under varying hydrological and physicochemical conditions exert also a significant role.