Despite COVID-19 impacts, 1st results are numerous.
WP1: Fieldwork campaigns were performed in order to collect samples of all environmental compartments (rocks, slags, sediments, soils, water, AMD, plants, mussels, fishes, etc.). Chemical (REE & other major and trace elements)and mineralogical & other types of analyses to identify the speciation of REE were performed to characterize the samples/sites, allowing the establishment of natural background & evaluation of the anthropogenic inputs, defining potential hotspots of REE contamination w/in the EU. The key role played by colloids in the speciation and transfer or REE was outlined in natural and experimental samples.The work performed allowed to establish the natural background of REE contents & distribution patterns in numerous contexts/environments. In most cases, anthropogenic modifications of the natural REE distribution in various environmental compartments could be recognized & defined, & 1st steps towards the quantification of anthropogenic REE input were made and notably REE bioaccumulation in plants recovered from old mining sites. The impact of mitigation/remediation processes implemented to improve water & soil quality could be characterized.
WP2: Determination of REE-reactive phase interactions at the molecular-level scale, represents an essential preliminary step to the complete understanding of REE transfer at macroscopic scale in the soil-water-living triptych. The transfer processes are then studied in systems, from the laboratory to the field-scale. Results obtained show the extraordinary variability of the REE patterns obtained in natural & synthetic systems & the strong dependence of these patterns on specific mineralogical phases. Discrepancy in REE interactions w/ living organisms are also shown since REE do not exhibit the same toxicity effect. Finally, we meet 2 objectives behind this work: (1) to evaluate & qualify the bioavailability & toxicity of REE through the development of a food web model, & (2) to provide insights for developing reactive transport models for the transfer of REE between different environmental compartments and therefore support policymakers in developing a sustainable and environmentally-friendly REE economy.
WP3: Most studies on ecotoxicological effects were done w/ microalgae & plants (La, Ce, & Gd were the most used) at concentrations between 0.01 & 140 mg L-1. The higher toxicity of free ions, which mainly appear at lower pH (as in mine discharge) confirms the high importance of metal speciation in ecotoxicity studies, as complexation of REE governs toxicity directly or indirectly. It was experimentally evidenced that : (i) Ln-PO4 precipitation would mask toxicity to algae,(ii)toxicokinetics & dynamics apparently differ between REE. HREE seem to be more toxic than LREE. s-XRF imaging of whole daphnids led to the hypothesis that more extensive distribution of Gd (HREE) compared to La (LREE) in the tissue, led to higher toxicity. An increased body burden was also shown through the analysis of field-collected mussels’ tissue & shells that showed up to 5 magnitudes higher concentration compared to the river water they came from. A species sensitivity distribution, resulted in the following prioritization list according to HC5 values in decreasing order: Yb > Eu > Dy > Ce > Y > Tb > Er > Gd > Pr > Nd > Lu > Sm > La. An effect of Ln concentrations already at naturally occurring concentrations can thus not be excluded. However, in environmental media, a lot of other cations would compete w/ Ln-ions for receptors on cellular surfaces. Occurring interrelationships are reflected by a biotic ligand model (BLM) for Daphnia magna. This work still in progress compare well to a BLM for Cd & show that Gd3+ & the H+ concentrations strongly govern toxicity. Chronic effects of environmentally relevant REE concentrations & their impact on different trophic levels were also studied and showed a slight stimulatory effect of REE exposure w/ regard to the onsite of reproduction & the doubling time of the daphnids population. Finally, different uptake routes have been also described for humans causing identifiable effects.
WP4: New insights into the molecular- and macroscopic-level processes controlling REE transport in natural porous media containing quartz sand, iron oxyhydroxides and/or colloids were provided. By combining batch and column experiments with surface complexation and reactive transport models, it was revealed that the mobility of REE is strongly affected by natural minerals under various conditions, using sand as immobile soil phase and/or colloid as mobile phase. Importantly, the investigated REE adsorption patterns provided crucial information on the key factors influencing mobility of multi-REE and analogous metals (Sc, Y, Th, U) in aqueous vs colloid transport. Furthermore, literature-based thermodynamic data for schwertmannite & basaluminite were incorporated to existing thermodynamic databases & preliminary calculations of REE speciation in acidic waters from Tharsis mine were performed through PHREEQC. The modelling revealed that REE predominate as sulfate complexes, i.e. LnSO4+ & as free trivalent metal cations (Ln3+) in all 3 AMD samples. In another study 2D geometry for the model of 1 of the landfills storing residues from phosphate industry was created. This geometry includes all the zones & introduces all the changes the landfill went through during the recent remediation. Along w/ the geometry, the gathered data includes the values of porosity, permeability, & other hydrogeological parameters for all the site’s zones. These simulations resulted in the basis of future assessments on the ecological impact of the release of REE into the environment.
