The Carbon-Sulfur Link in the Remineralization of Organic Carbon in Surface Sediments

Frontiers in Earth Science

卷:9

Duygu S. Sevilgen¹  Harold J. Bradbury²  Alexandra V. Turchyn²  Angus Fotherby²  David A. Hodell²  Mervyn Greaves²  Jennifer L. Druhan⁴  Adam Bateson⁵  Gilad Antler⁶ 

[1] Centre Scientifique de Monaco, Monaco, Monaco;

[2] Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom;

[3] Department of Earth and Environmental Sciences, Ben Gurion University of the Negev, Beersheba, Israel;

[4] Department of Geology, University of Illinois at Urbana Champaign, Urbana, IL, United States;

[5] Department of Meteorology, University of Reading, Reading, United Kingdom;

[6] The Interuniversity Institute for Marine Sciences in Eilat, Eilat, Israel;

关键词: carbon isotopes;    sulfur isotopes;    early diagenesis;    microbial sulfate reduction;    methanotrophy and methanogenesis;    reactive transport modeling;   

DOI  :  10.3389/feart.2021.652960

来源: DOAJ

【 摘 要 】

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 δ13CDIC vs. δ34SSO4 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 δ13CDIC vs. δ34SSO4 cross plot. The δ13C of the DIC released during sulfate reduction and sulfate-driven anaerobic oxidation of methane is a major control on the minimum δ13CDIC value in the δ13CDIC vs. δ34SSO4 cross plot, with the δ13C of the organic carbon being important during both MSR and combined sulfate reduction, sulfate-driven AOM and methanogenesis.

【 授权许可】

Unknown