Goldschmidt 2019 conference session: Trace Elements Speciation: Novel Methodologies and Insights into Transformations Influencing their Global Biogeochemical Cycle

Many trace elements (TE) can be toxic (e.g., As, Hg, Sb) and/or essential (e.g., Cu, I, Se) for humans, plants and wildlife. Some also play important roles in atmospheric processes, e.g., S, I and Br. To understand the biogeochemical cycle and effects of TE, it is crucial not only to quantify them in environmental and biological compartments, but also to determine their speciation. This entails the distribution of TE between specific chemical forms in term of electronic or oxidation state, molecular structure or complexes formed with various ligands. Indeed, the partitioning, transport, bioavailability, bioaccumulation and toxic or beneficial effects of TE largely depend on their speciation. The goal of this session is to highlight recent advances (1) in methodologies, using elemental, molecular and/or spectroscopic techniques, allowing the identification and/or quantification of TE species (2) in our mechanistic understanding of the biotic and/or abiotic transformations affecting TE species (e.g., alkylation/dealkylation, oxidation/reduction, colloid formation and sorption/desorption) and (3) in assessing fluxes of TE among aquatic, terrestrial and atmospheric (eco)systems. Contributions to the session may include fundamental and applied research based on laboratory work, field experiments and/or modeling approaches. Studies looking at the potential effects of on-going and future global changes, such as climate change and eutrophication, on the fate of TE and their species are also strongly encouraged.