Pore-water and solid-phase trace metals from sediment cores during SONNE cruises SO268/1 and SO268/2, central Pacific@en

Physical and chemical trace metal speciation are important for our understanding of metal cycling and potential toxicity to marine life. Trace metals can have different bioavailabilities and behave differently in diffusion processes or particle-solution interactions depending on their physical and chemical forms. Here we investigated dissolved (< 0.2 µm) and soluble (< 0.02 µm) concentrations of Mn, Fe, Co, Ni, Cu, V, Mo, U, Cd, and As in oxic and suboxic deep-sea sediments of the central equatorial Pacific. Additionally, surface sediments from selected cores were analyzed for solid-phase Mn to assess potential Mn (and associated metal) mobilization into the pore water from the solid phase during early diagenesis. Vanadium, Mo, U, Cd, and As showed no significant difference between the dissolved and soluble concentrations suggesting that they are present in the truly dissolved or small colloidal fraction. The same was true for Mn and Co in suboxic pore waters. In contrast, the colloidal fraction (> 0.02 µm < 0.2 µm) of Cu increased with depth as well as the colloidal fraction of Mn, Co, and Ni in oxic pore waters. Fe had the largest but variable colloidal pool. Samples were taken during the SO268 cruise to the German and Belgian license areas for polymetallic nodule mining in the Clarion Clipperton Fracture Zone as part of the MiningImpact project. Sediment cores were collected with multicorers (MUC), ROV push cores (PUC), and gravity corers (GC). Pore water was extracted by means of centrifugation and sequential filtration using cleaned polyethersulfone (PES) syringe filters (0.2 µm) and Anopore syringe filters (0.02 µm). Pore water was preserved by acidification to ~ pH 1.8 with concentrated ultrapure HCl. Mn, Fe, Co, and Ni were measured by High Resolution Sector Field Inductively Coupled Plasma-Mass Spectrometry at GEOMAR, Kiel, Germany and Cu, V, Mo, U, Cd, and As as well as Mn and Co in the GCs by Inductively Coupled Plasma-Mass Spectrometry at Jacobs University Bremen, Germany (now Constructor University). Solid-phase samples from which the pore water was previously extracted were freeze-dried and acid pressure digested using HF and HClO4. Manganese was then analyzed in the digestion solutions with an Inductively Coupled Plasma Optical Emission Spectrometer at Jacobs University Bremen, Germany.痕量金属物理化学形态（trace metal speciation）对于我们理解金属循环及其对海洋生物的潜在毒性至关重要。痕量金属的物理化学形态不同，其生物可利用性存在差异，在扩散过程或颗粒-溶液相互作用中的行为模式亦有所区别。本研究针对赤道太平洋中部含氧、次含氧深海沉积物，分析了Mn、Fe、Co、Ni、Cu、V、Mo、U、Cd及As的溶解态（<0.2 µm）与可溶性（<0.02 µm）浓度。此外，本研究还对选定岩芯的表层沉积物开展固相Mn分析，以评估早期成岩作用（early diagenesis）期间，固相Mn（及其伴生金属）向孔隙水（pore water）迁移的潜在可能性。钒（V）、钼（Mo）、铀（U）、镉（Cd）及砷（As）的溶解态与可溶性浓度无显著差异，表明它们以真溶解态或小胶体组分（colloidal fraction）形式存在。次含氧孔隙水中的Mn与Co亦呈现相同规律。与之相反，含氧孔隙水中Cu的胶体组分（>0.02 µm且<0.2 µm）随深度增加而升高，Mn、Co及Ni的胶体组分亦呈现类似变化趋势。铁（Fe）的胶体库规模最大，但组分占比存在波动。本研究的样品采集自德国与比利时在克拉里昂-克利珀顿断裂带（Clarion Clipperton Fracture Zone）的多金属结核（polymetallic nodule）采矿许可海域SO268航次，为MiningImpact项目的组成部分。沉积物岩芯通过多管取样器（multicorers, MUC）、遥控水下机器人推取岩芯（ROV push cores, PUC）及重力取样器（gravity corers, GC）采集。孔隙水通过离心法提取，并经净化后的聚醚砜（polyethersulfone, PES）针式过滤器（0.2 µm）与Anopore针式过滤器（0.02 µm）依次过滤。孔隙水经浓缩超纯盐酸酸化至pH≈1.8进行保存。Mn、Fe、Co及Ni的浓度在德国基尔GEOMAR研究所通过高分辨扇形场电感耦合等离子体质谱（High Resolution Sector Field Inductively Coupled Plasma-Mass Spectrometry）测定；Cu、V、Mo、U、Cd及As，以及重力取样器（GC）样品中的Mn与Co，则在德国不来梅雅各布大学（现为不来梅Constructor大学）通过电感耦合等离子体质谱（Inductively Coupled Plasma-Mass Spectrometry）测定。此前已提取孔隙水的固相样品经冷冻干燥后，采用氢氟酸（HF）与高氯酸（HClO4）开展酸压消解。消解液中的Mn浓度则在德国不来梅雅各布大学（现为不来梅Constructor大学）通过电感耦合等离子体光发射光谱仪（Inductively Coupled Plasma Optical Emission Spectrometer）测定。