CHROMA · Mobilization of chromium by organic matter in reduced systems
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2022-07-01 → 2024-06-30
- EU contribution
- €174,167
- Participants
- 1
- Scheme
- MSCA-IF
Lines connect the coordinator with its partners.
Results in brief
Mobilization of chromium by organic matter in reduced systems
Chromium (Cr) has received considerable attention for its potential toxicity to human beings, as well as its utilisation as a tracer for redox processes operating in Earth’s critical zones and in ocean sediments. Chromium has two stable oxidation states, hexavalent Cr(VI) and trivalent Cr(III), which are respectively soluble and insoluble. Whilst reduction of Cr(VI) largely shapes the Cr distribution in natural environments (and has thus been adopted as a pollution mitigation strategy), redox transformations alone cannot fully explain the geochemical behaviour of Cr. For example, in surface waters, dissolved Cr concentrations are usually higher than predicted by the solubility of Cr minerals, suggesting additional ‘stabilisation’ mechanisms. We need to appraise the role of small organic molecules called ligands, which have been invoked to control the mobilisation, transport and fate of many heavy metals. This project combines an interdisciplinary set of field sampling, controlled experiments, isotopic analysis alongside geochemical modelling, to ground-truth the hypotheses that (i) solid Cr can be effectively remobilised by organic ligands in reducing environment despite Cr reduction, and (ii) aqueous Cr can be stabilised in the form of organic complexes with distinct Cr isotopic signature. Addressing these questions is important to the geosciences community as well as the wider public. Firstly, as Cr is a known carcinogen, increased levels of organic ligands, such as in paddy field systems, will potentially cause increased ecological and health risks. Secondly, organic ligands play an overlooked role in modulating the input and removal processes of dissolved Cr to/from various environments (including weathering, benthic, and hydrothermal fluxes), which are poorly constrained to date. Lastly, Cr isotopes are proven as promising tool to fingerprint ligand-bound Cr(III) that has been difficult to characterise/quantify with conventional analytical approaches.
Data: CORDIS, © European Union
Project objective
Long-term pollution mitigation requires a better understanding of the biogeochemical processes that regulate the behavior and fate of trace metals, such as chromium (Cr), in subsurface environments. The emerging role of organic ligands, including siderophores and organic acids, in the speciation, bioavailability and mobility of trace metals is receiving increasing attention. However, the relative importance of the opposing Cr reduction and mobilization processes in sediments remain poorly constrained, and the Cr-ligand interaction has not been explicitly determined. Whilst stable isotope compositions of Cr are an effective tool for assessing biogeochemical cycling and redox processes, there have been few studies reporting the isotope effect of ligand-induced Cr mobilization. This project combines an interdisciplinary set of field sampling, controlled experiments, isotopic analysis alongside geochemical modelling, aiming to test the hypothesis that (1) solid Cr can be effectively remobilized by organic matter in reduced environment despite Cr reduction, and (2) aqueous Cr can be stabilized in the form of organic complexes with a distinct Cr isotope signature. The extent and mechanism of Cr mobilization by organic ligands under various environmental conditions will be quantified. Stable Cr isotopes in sediment pore water will be accurately determined and validated as a tracer for Cr-ligand complexation. The fate of Cr in relation to Fe and organic ligands in sediments will be predicted. This project will shed new light on the role of organic ligands in the Cr redox cycle, and will reveal the sensitivity of subsurface environments to anthropogenic activities. This project includes both the transfer of knowledge to the host institution and the training of the candidate in advanced techniques. Results from this project will be disseminated to the environmental science and geochemistry research community and to the wider public.
Original text from CORDIS.
Participants
- UNIVERSITAT WIEN · WienCoordinatorAustria
Links
- View on CORDIS
- DOI: 10.3030/101031974
- https://edge.univie.ac.at/research/current-projects/detail-view/news/mobilization-of-chromium-by-organic-matter-in-reduced-systems-chroma/
Data: CORDIS, © European Union