Marine sediments are an important source and sink of bio-essential trace metals to the ocean. However, the different mechanisms leading to trace metal release or burial are not fully understood and the associated fluxes are not well quantified. Here, we present sediment, pore water, sequential extraction and benthic flux data of Mn, Co, Ni, Cu, Zn and Cd along a latitudinal depth transect across the Peruvian oxygen minimum zone at 12°S. Sediments are depleted in Mn and Co compared to the lithogenic background. Diffusive Mn fluxes from the sediments into the bottom water (−26 to −550 μmol m⁻² y⁻¹) are largely consistent with the rate of Mn loss from the solid phase (−100 to −1160 μmol m⁻² yr⁻¹) suggesting that 50% or more of the sedimentary Mn depletion is attributed to benthic efflux. In contrast, benthic Co fluxes (~ −3 μmol m⁻² yr⁻¹) are lower than the rate of Co loss from the solid phase (up to −120 μmol m⁻² yr⁻¹), implying Co dissolution in the water column. The trace metals Ni, Cu, Zn and Cd are enriched within the sediments with respect to the lithogenic background. Uptake of Ni by phytoplankton in the photic zone and delivery with organic matter to the sediment surface can account for up to 100% of the excess Ni accumulation (87 to 180 μmol m⁻² y⁻¹) in shelf sediments near the coast, whereas at greater water depth additional scavenging by Mn- and Fe-oxides may contribute to Ni accumulation. Up to 20% of excess Cu (33 to 590 μmol m⁻² y⁻¹) and generally less than 20% of excess Zn (58 to 2170 μmol m⁻² y⁻¹) and Cd (6 to 260 μmol m⁻² y⁻¹) can be explained by delivery with fresh organic matter. Sequential extraction data suggest that the discrepancies between the known sources of Cd (and Cu) and their excess accumulation may be driven by the delivery of allochthonous sulphide minerals precipitated from the water column. Additionally, Cu may be scavenged by downward sinking organic material. In contrast, precipitation of Zn sulphide chiefly takes place in the sediment. Diffusive Zn fluxes into the sediment (21 to 1990 μmol m⁻² y⁻¹) match the excess Zn accumulation suggesting that Zn delivery is mediated by molecular diffusion from bottom waters. Considering the diverse behavioural pattern of trace metals observed in this study, we argue that declining oxygen and increasing hydrogen sulphide concentrations in a future ocean will modify trace metal fluxes at the seafloor and the trace metal stoichiometry of seawater.

海洋沉积物是生物必需的微量金属向海洋的重要来源和汇聚处。然而，导致痕量金属释放或埋葬的不同机制尚未完全理解，并且相关的通量也未得到很好的量化。在这里，我们介绍了在12°S时横跨秘鲁最小氧区的纬向深度横断面的Mn，Co，Ni，Cu，Zn和Cd的沉积物，孔隙水，顺序提取和底栖通量数据。与成岩本底相比，沉积物中的锰和钴减少了。从沉积物中到底部水中的扩散锰通量（-26至-550μmolm ^-2 y ^-1）与固相中锰的损失速率（-100至-1160μmolm ^-2  yr ^-1）基本一致）表明50％或更多的沉积Mn耗竭归因于底栖外排。相比之下，底栖的Co通量（〜^-  3μmolm ^-2 yr ^-1）低于固相中Co的损失率（最高-120μmolm ^-2  yr ^-1 ），这意味着Co在水中的溶解柱子。相对于成岩本底，痕量金属Ni，Cu，Zn和Cd富集在沉积物中。在光合作用区的浮游植物对镍的吸收以及有机物向沉积物表面的输送最多可占多余镍累积量的100％（87至180μmolm ^-2 y ^-1）在沿海附近的陆架沉积物中，而在更大的水深中，Mn和Fe氧化物的额外清除可能会促进Ni的积累。最多20％的过量Cu（33至590μmolm ^-2 y ^-1）和通常少于20％的过量Zn（58至2170μmolm ^-2 y ^-1）和Cd（6至260μmolm ^-2） y ^-1）可以通过与新鲜有机物一起运输来解释。连续提取数据表明，已知的Cd（和Cu）来源与其过量积累之间的差异可能是由从水柱中沉淀出来的异质硫化物矿物的输送所驱动。另外，可以通过向下沉的有机材料清除Cu。相反，硫化锌的沉淀主要发生在沉积物中。进入沉积物中的扩散锌通量（21至1990μmolm ^-2 y ^-1 ）与过量的锌积累相匹配，这表明锌的输送是通过从底水的分子扩散来介导的。考虑到本研究中观察到的痕量金属的多种行为模式，我们认为氧气下降而硫化氢增加未来海洋中的浓度会改变海底的痕量金属通量和海水的痕量金属化学计量。