Fortin, Claude
The biogeochemical fate of rare earth elements in aquatic ecosystems
Rare earth elements (REEs) are in high demand globally for the green transition and high technologies. The growing demand leads to their release into aquatic ecosystems from various point and non-point sources, which creates urgency to investigate their fate and enrichment. This thesis further investigates the biogeochemical fate and REE uptake mechanisms throughout aquatic ecosystems. Rare earth element concentrations and fractionations were quantified to determine the natural uptake mechanism of three REE exposure pathways (dissolved, diet, and particulate) into aquatic organisms. Pelagic organisms accumulated heavy REEs, indicating they primarily uptake dissolved REEs. Benthic organisms were characterized by REE patterns specific for diet and particulate REEs. Furthermore, lanthanum (La) enrichment was investigated in a lake treated with La-based coagulants using La anomalies. Lanthanum enrichment in the water and organisms were directly related to La dispersion from sediments. This research provides information on preferential exposure pathways and REE enrichment in aquatic ecosystems.
Author Keywords: bioaccumulation potential, fractionations, lanthanum enrichment, metal organotropism, rare earth elements, uptake mechanisms