Paul, Sophie Anna Luise; Koschinsky, Andrea: Dissolved and soluble pore water trace metals from sediment core SO268/1_84-1 (GC-05) during SONNE cruise SO268/1, central Pacific [dataset]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.955676 (dataset in review)

We compare trace metal (Mn, Co, Cu, V, Mo, U, Cd, and As) cycling in the upper ca. 5 m of the German and Belgian license areas for polymetallic nodule mining in the Clarion Clipperton Zone in the Pacific Ocean. Considerable differences can be observed based on redox conditions, leading to Mn oxide dissolution of the solid phase as well as buried polymetallic nodules. Mobilization of metals to the pore water varies between the study sites. Interesting observations were made for Molybdenum (Mo): In the German area, dissolved Mo concentrations reached up to ca. 250 nmol/kg, while in the Belgian area, concentrations rarely rose above 100 nmol/kg. Additionally, 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 bioavailability and behave differently in diffusion processes or particle-solution interactions depending on their physical and chemical forms. Here we also investigated dissolved (< 0.2 µm) and soluble (< 0.02 µm) concentrations in oxic and suboxic deep-sea sediments of the central equatorial Pacific. Vanadium, Mo, U, Cd, and As showed no significant difference between the dissolved and soluble concentrations suggesting that they are present as inorganic ionic species or organic complexes either 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. Samples were taken during the SO268 cruise as part of the MiningImpact project. Sediment cores were collected with ca. 5 m long 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. Samples were measured by Inducitvely Coupled Plasma-Mass Spectrometry.