ECOTREE

Rare Earth Elements (REEs) are used in high-tech devices and other military and agricultural applications. Anthropogenic use is disrupting the biogeochemical cycle and enrichments of La, Ce, Nd, Sm and Gd are already detectable in waters. The current literature on REE-associated health effects is mostly confined to three REE, thus the information for several REE remains relatively scarce, not withstanding their growing industrial utilization and, hence, environmental spread and human exposures. So far, no regulatory thresholds for REE concentrations and emissions to the environment have been set because information on risks from REE is scarce. However, evidence gathers that REEs have to be acknowledged as new, emerging contaminants with manifold ways of entry into the environment. No consensus exists as to whether the ecotoxicity of REEs varies in a predictable way, as it happens for their atomic properties. Such consensus is actually critical considering that all REE likely share a common mechanism of action with potentially additive effects on living organisms. ECOTREE is a multidisciplinary project organized in 8 Work Packages to generate results for a complete understanding of the relationship between REE occurrence in water systems, their dynamics and speciation, the exposure pathway of aquatic species and their environmental impacts developed in an AOP framework. The relative abundance of REEs, the presence of anthropogenic anomalies and their origin will be investigated in rivers ecosystems, in order to correctly understand and reproduce them in controlled laboratory conditions. Particular attention will be given to REE speciation and to the partitioning of REE between suspended matter, colloids and true solution in the water column. Formation of insoluble species may create different types of fractionation on the REE and affect the distribution of the different REE in the labile fractions of the water. General toxicity patterns for individual aquatic organisms will be identified; so that bioavailability and bioaccumulation investigations can be focussed on selected elements representative of the entire REE series. A variety of toxicity endpoints at different level of biological organization will be considered: molecular and cellular effects (daphnids, fish and bivalve cell lines), individual and population relevant effects (algae, aquatic plants, daphnids, bivalves, fish), effects on functional processes such as filtration in bivalves, or oxygen consumption in species. ‘Omics’ technology in particular transcriptomic and proteomic approaches will be applied on daphnids to gain mechanistic understanding of the induced toxicity. The importance of different routes of exposure, the influence of organic matter for the behaviour of the model elements will be verified. In particular, attention will be devoted to the study of REE uptake in the presence and absence of model organic colloids. The latter experiment will also allow the investigation of trophic transfer. Bioaccumulation approaches based on sub-cellular fractionation and synchrotron will be applied to understand cell localisation and speciation of contaminants helping to understand how accumulation relates to toxic effects.Finally, we will investigate the integration of the results into a Life Cycle Assessment (LCA) framework, in particular ecotoxicity assessment, using the reference model UseTox®. The aim is to develop novel ecotoxicity characterization factors (CFs) for the selected REEs. These CFs would allow evaluating the impacts of REEs contained in wastewater when released into the environment. Results of ECOTREE experiments will provide new knowledge to fill critical gaps on the potential for environmental impact of REE on freshwater ecosystems. It will provide environmental managers and policy makers with information that can be directed towards hazard classification of material containing REEs as well as risk assessments in contaminated environments.