Elucidating global biogeochemical cycles in the past and present by characterizing trace metal speciation using voltammetry

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The distribution and chemical speciation of trace elements in the oceans plays a key role in determining marine productivity and influencing global biogeochemical cycles. For example, the rate of production and consumption of many 'climate-active' gases (e.g. carbon dioxide, nitrous oxides and methane) by marine microorganisms is regulated by the bio-availability of essential trace metals such as iron and copper. Furthermore, the isotopic composition of trace metals in ancient marine sediments, which is affected by chemical speciation, can be used as proxies of past earth events (e.g. ocean anoxia). Investigating the distribution and chemical speciation of trace elements is thus essential for our understanding of global biogeochemical cycles in the past and present. Our research integrates laboratory and field studies to examine how the speciation of trace elements affects marine microbial processes, and the interpretation of isotope tracers in marine sediments. We also investigate how microbial processes influence trace metal bio-availability by enzyme-mediated redox reactions at the cell surface, by the release of organic metal-bind complexes, and by mediating mineral formation. A critical component of this research is the determination of trace metal concentrations and chemical speciation both in field samples and laboratory culture experiments. This proposal request funds to purchase a BASi voltammetric system, which uses cyclic voltammetry to provide qualitative and quantitative information on the speciation of dissolved trace metals, including their oxidation state, the concentration of dissolved metals and their organic complexes, as well as the stability constants of these metal complexes.