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  • Frontiers Media SA  (2)
  • 1
    Online Resource
    Online Resource
    Table_3.XLSX
    Frontiers Media SA ; 2021
    In:  Frontiers in Earth Science Vol. 9 ( 2021-4-30)
    Details
    In: Frontiers in Earth Science, Frontiers Media SA, Vol. 9 ( 2021-4-30)
    Abstract: Here we present the carbon isotopic composition of dissolved inorganic carbon (DIC) and the sulfur isotopic composition of sulfate, along with changes in sulfate concentrations, of the pore fluid collected from a series of sediment cores located along a depth transect on the Iberian Margin. We use these data to explore the coupling of microbial sulfate reduction (MSR) to organic carbon oxidation in the uppermost (up to nine meters) sediment. We argue that the combined use of the carbon and sulfur isotopic composition, of DIC and sulfate respectively, in sedimentary pore fluids, viewed through a δ 13 C DIC vs. δ 34 S SO4 cross plot, reveals significant insight into the nature of carbon-sulfur coupling in marine sedimentary pore fluids on continental margins. Our data show systemic changes in the carbon and sulfur isotopic composition of DIC and sulfate (respectively) where, at all sites, the carbon isotopic composition of the DIC decreases before the sulfur isotopic composition of sulfate increases. We compare our results to global data and show that this behavior persists over a range of sediment types, locations and water depths. We use a reactive-transport model to show how changes in the amount of DIC in seawater, the carbon isotopic composition of organic matter, the amount of organic carbon oxidation by early diagenetic reactions, and the presence and source of methane influence the carbon and sulfur isotopic composition of sedimentary pore fluids and the shape of the δ 13 C DIC vs. δ 34 S SO4 cross plot. The δ 13 C of the DIC released during sulfate reduction and sulfate-driven anaerobic oxidation of methane is a major control on the minimum δ 13 C DIC value in the δ 13 C DIC vs. δ 34 S SO4 cross plot, with the δ 13 C of the organic carbon being important during both MSR and combined sulfate reduction, sulfate-driven AOM and methanogenesis.
    Type of Medium: Online Resource
    ISSN: 2296-6463
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.3389/feart.2021.652960
    DOI: 10.3389/feart.2021.652960.s001
    DOI: 10.3389/feart.2021.652960.s002
    DOI: 10.3389/feart.2021.652960.s003
    DOI: 10.3389/feart.2021.652960.s004
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2741235-0
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Table1.XLSX
    Frontiers Media SA ; 2021
    In:  Frontiers in Earth Science Vol. 9 ( 2021-8-5)
    Details
    In: Frontiers in Earth Science, Frontiers Media SA, Vol. 9 ( 2021-8-5)
    Abstract: We present pore fluid geochemistry, including major ion and trace metal concentrations and the isotopic composition of pore fluid calcium and sulfate, from the uppermost meter of sediments from the Gulf of Aqaba (Northeast Red Sea) and the Iberian Margin (North Atlantic Ocean). In both the locations, we observe strong correlations among calcium, magnesium, strontium, and sulfate concentrations as well as the sulfur isotopic composition of sulfate and alkalinity, suggestive of active changes in the redox state and pH that should lead to carbonate mineral precipitation and dissolution. The calcium isotope composition of pore fluid calcium (δ 44 Ca) is, however, relatively invariant in our measured profiles, suggesting that carbonate mineral precipitation is not occurring within the boundary layer at these sites. We explore several reasons why the pore fluid δ 44 Ca might not be changing in the studied profiles, despite changes in other major ions and their isotopic composition, including mixing between the surface and deep precipitation of carbonate minerals below the boundary layer, the possibility that active iron and manganese cycling inhibits carbonate mineral precipitation, and that mineral precipitation may be slow enough to preclude calcium isotope fractionation during carbonate mineral precipitation. Our results suggest that active carbonate dissolution and precipitation, particularly in the diffusive boundary layer, may elicit a more complex response in the pore fluid δ 44 Ca than previously thought.
    Type of Medium: Online Resource
    ISSN: 2296-6463
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.3389/feart.2021.601194
    DOI: 10.3389/feart.2021.601194.s001
    DOI: 10.3389/feart.2021.601194.s002
    DOI: 10.3389/feart.2021.601194.s003
    DOI: 10.3389/feart.2021.601194.s004
    DOI: 10.3389/feart.2021.601194.s005
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2741235-0
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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