Colloidal transport and seasonal variations of technology critical elements in aquatic systems

Technology critical elements (TCEs) are widely understudied in aquatic systems. Many unknowns particularly are linked to the mechanistic understanding of TCE transport mechanisms in contrasting river systems. In this work, we aim at characterizing the colloidal vs truly dissolved TCE concentrations in three contrasting rivers in Germany (Rhine, Neckar and Danube) by comparing two filtering meshes (0.45 vs 0.02 µm). The seasonal component of such transport is also investigated based on monthly collections of water samples in 2023. TCEs were analysed via external calibration at the ICP-MS (iCAP series, Thermo®). Results suggest that each river has a different load on TCE concentrations, of which the colloidal transport differs even within the Rare Earth Elements and Yttrium (REEY) list. The seasonal influence is compared to water discharges and temperature ranges. These results provide further understanding of the watershed dynamics and can help identifying relevant processes that determine the unknown aquatic transport and fate of TCEs. This information can be used for developing scenarios for potential risk assessment of anthropogenic discharges from both stable and/or radioactive origin in surface aquatic environments in Germany.

Acknowledgements:

This work was funded by the Federal Ministry of Education and Research (BMBF) and the Baden-Württemberg Ministry of Science as part of the Excellence Strategy of the German Federal and State Governments. The authors also acknowledge the extensive contribution of the Landesanstalt für Umwelt Baden-Württemberg (LUBW, Germany) and the Amt für Umwelt und Energie (AUE, Switzerland) for the collection of water samples.