Paul, Sophie Anna Luise; Schmidt, Katja; Achterberg, Eric Pieter; Koschinsky, Andrea (2024): Pore-water and solid-phase trace metals from sediment cores during SONNE cruises SO268/1 and SO268/2, central Pacific [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.965035

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.