Anna-Lena Zocher

• Our modern society relies heavily on the availability and utilisation of rare earth elements and yttrium (REY) for high-tech products and processes, which provokes a growing release of these metals into the environment and draws attention to biological and ecotoxicological consequences of their increasing concentrations in the environment. However, research has long neglected the environmental behaviour of REY. Coupled with publications including incomplete REY sets or data of questionable analytical quality, many open questions remain. This dissertation investigates samples from the biosphere and from the hydrosphere to shed light on the REY transfer at their interface. Duckweeds, widely occurring small water plants, and Norwegian fjord waters together with Baltic Sea outflow samples were chosen as main study objects from the biosphere and the hydrosphere, respectively. The findings of the biosphere-focused part improve the characterisation of the duckweed reference material BCR-670 (Lemna minor) and highlight the necessity of comparable sample processing for validation of data quality. All naturally grown duckweeds investigated are REY quasi-hyperaccumulators and share similarly shaped, mildly fractionated shale-normalised REY patterns without positive anthropogenic Gd anomalies, regardless of whether they grew in waters with or without anomalous Gd enrichment. The hydrosphere-focused part presents the first evidence for constant anthropogenic Gd input into the Baltic Sea outflow. The data combined with literature data further suggest that this signal is transported to southern Norway. In future, it may reach fjord waters further north along the Norwegian coast. Overall, this dissertation provides important new information about the fate of geogenic and anthropogenic REY at the hydrosphere-biosphere interface and highlights the relevance of basic research as the basis for understanding the complex REY transfer mechanisms across environmental compartments.