Porewater sulfate and sulfide concentrations in Alvin pushcore samples collected from Guaymas Basin hydrothermal vents during R/V Atlantis cruise AT42-05 in November 2018 and analyzed at UNC Chapel Hill (NCEI Accession 0278662)

Acquisition Description:
This porewater dataset was obtained by Chris Chambers at the University of North Carolina Chapel Hill. The sampling site names in the data are based on Teske et al. 2016.

For analysis at UNC (Chris Chambers), porewater was obtained from freshly collected sediment push cores on R/V Atlantis. The sediment cores were sampled in 3 cm intervals; ca. 40 ml sediment samples were centrifuged in 50 ml conical Falcon tubes for 5 to 10 minutes at approx. 1000 g, until the sediment had settled and produced ca. 8 to 10 ml of porewater. The sediment interval depths are given in the dataset (Sediment_depth). For porewater sulfide analysis, 1 ml porewater subsamples were drawn into syringes, filtered immediately through 0.45 μm filters, and placed in Eppendorf sample vials each containing 0.1 ml of 0.1 M zinc acetate solution to preserve the sulfide as zinc sulfide until analyzed. Sulfide was quantified spectrophotometrically at UNC-Chapel Hill using the methylene blue method (Cline 1969). For sulfate analysis, 1 ml porewater samples were acidified with 50 microliters of 1 N HCl, and bubbled with N2 for 1 minute to remove hydrogen sulfide. After returning the samples to the home laboratory, sulfate concentrations were determined using the ion chromatograph of the UNC Environmental Program.

Problem report: Transport problems have caused sample losses among the porewater samples, which are evident in occasional gaps in porewater profiles.