Input, particle reactivity, and (bio)geochemical cycling of the transition metals from subgroups IV, V, and VI (Ti-Zr-Hf, V-Nb-Ta, Cr-Mo-W) in the Atlantic

本文研究的重点是海洋地球化学中微量元素群Ti-Zr-Hf、V-Nb-Ta和Cr-Mo-W，这些元素在海水中的行为和过程尚不清楚。然而，它们在海洋系统中具有重要的生物学意义（作为微量营养素或微毒素），或有助于在海底形成有价值的矿床，如锰铁结核和结壳。其中一些还可以（特别是通过它们的同位素特征）作为元素来源进入海洋、水团运动或古氧化还原条件的代用物。相应地，将研究粉尘或河流源以及随后的（生物）地球化学循环对前两组颗粒活性元素的影响，以及氧最小区不同氧化还原条件对氧化还原敏感元素组（Cr, Mo，与W相反）的影响。除了列出的9种元素外，我们还将包括Al（作为粉尘输入的示踪剂），Fe（作为铁氧化物形式的潜在痕量金属清除剂），Y（作为表征良好的颗粒反应元素）和U（与地球化学相似的Mo进行比较）来解释来源和循环。该项目的样本是在M81/1号巡航期间，通过对大西洋上17个CTD站的水柱进行痕量金属清洁采样而获得的。除了确定总浓度外，物理（溶解-胶体-颗粒）和化学形态分析（自由离子，有机络合物，氧化还原形态）将是工作计划的一部分。

The focus of this proposal is the marine geochemistry of the trace element groups Ti-Zr-Hf, V-Nb-Ta, and Cr-Mo-W, elements of which the behavior and processes in seawater are partly not well understood. However, they are of importance in the marine system either biologically (as micronutrients or microtoxins), or contribute to the formation of valuable ore deposits on the seafloor, such as ferromanganese nodules and crusts. Several of them also serve (especially via their isotopic signatures) as proxies for elemental sources into the ocean, water mass movements, or paleo redox conditions. Correspondingly, the impact of dust or riverine sources and subsequent (bio)geochemical cycling of the particle-reactive elements of the first two groups, and of different redox conditions in the oxygen minimum zone on the group of redox-sensitive elements (Cr, Mo, in contrast to W), will be investigated. Apart from the listed 9 elements, we will include Al (as a tracer for dust input), Fe (as a potential trace metal scavenger in the form of Fe oxyhydroxides), Y as a well characterized particle -reactive element, and U (to compare with the geochemically similar Mo) to interpret sources and cycling. The samples for the project were taken by trace-metal clean sampling of the water column at 17 CTD stations across the Atlantic during cruise M81/1. Apart from the determination of total concentrations, physical (dissolved – colloidal – particulate) and chemical speciation analyses (free ions, organic complexes, redox speciation) will be part of the work schedule.