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

海洋中微量元素的分布和化学形态在决定海洋生产力和影响全球生物地球化学循环方面发挥着关键作用。例如，海洋微生物产生和消耗许多“气候活性”气体(如二氧化碳、一氧化二氮和甲烷)的速度受铁和铜等必需痕量金属的生物可获得性的制约。此外，古代海洋沉积物中痕量金属的同位素组成受化学形态的影响，可以作为过去地球事件(如海洋缺氧)的代用品。因此，研究微量元素的分布和化学形态对于我们理解过去和现在的全球生物地球化学循环是至关重要的。我们的研究结合了实验室和现场研究，以检查微量元素的形态如何影响海洋微生物过程，以及海洋沉积物中同位素示踪剂的解释。我们还研究了微生物过程如何通过酶介导的细胞表面氧化还原反应、有机金属结合络合物的释放以及通过介导矿物形成来影响痕量金属的生物有效性。这项研究的一个关键组成部分是确定野外样品和实验室培养实验中的痕量金属浓度和化学形态。这项提案要求资金购买基本伏安法系统，该系统使用循环伏安法提供有关溶解痕量金属形态的定性和定量信息，包括其氧化态、溶解金属及其有机络合物的浓度以及这些金属络合物的稳定常数。

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.