Global-scale quantification of mineralization pathways in marine sediments: A reaction-transport modeling approach
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In this article, a numerical modeling approach is used as an alternative to quantify the major metabolic pathways of Corg oxidation (Cox) and associated fluxes of redox-sensitive species fluxes along a global ocean hypsometry, using the seafloor depth (SFD) as the master variable.Abstract:
[1] The global-scale quantification of organic carbon (Corg) degradation pathways in marine sediments is difficult to achieve experimentally due to the limited availability of field data. In the present study, a numerical modeling approach is used as an alternative to quantify the major metabolic pathways of Corg oxidation (Cox) and associated fluxes of redox-sensitive species fluxes along a global ocean hypsometry, using the seafloor depth (SFD) as the master variable. The SFD dependency of the model parameters and forcing functions is extracted from existing empirical relationships or from the NOAA World Ocean Atlas. Results are in general agreement with estimates from the literature showing that the relative contribution of aerobic respiration to Cox increases from 80% in deep-sea sediments. Sulfate reduction essentially follows an inversed SFD dependency, the other metabolic pathways (denitrification, Mn and Fe reduction) only adding minor contributions to the global-scale mineralization of Corg. The hypsometric analysis allows the establishment of relationships between the individual terminal electron acceptor (TEA) fluxes across the sediment-water interface and their respective contributions to the Corg decomposition process. On a global average, simulation results indicate that sulfate reduction is the dominant metabolic pathway and accounts for approximately 76% of the total Cox, which is higher than reported so far by other authors. The results also demonstrate the importance of bioirrigation for the assessment of global species fluxes. Especially at shallow SFD most of the TEAs enter the sediments via bioirrigation, which complicates the use of concentration profiles for the determination of total TEA fluxes by molecular diffusion. Furthermore, bioirrigation accounts for major losses of reduced species from the sediment to the water column prohibiting their reoxidation inside the sediment. As a result, the total carbon mineralization rate exceeds the total flux of oxygen into the sediment by a factor of 2 globally.read more
Citations
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Quantifying the degradation of organic matter in marine sediments: A review and synthesis
Sandra Arndt,Sandra Arndt,Bo Barker Jørgensen,Douglas E. LaRowe,Jack J. Middelburg,Richard D. Pancost,Pierre Regnier +6 more
TL;DR: In this paper, a review of recent developments in the quantitative modeling of organic matter degradation in marine sediments is critically reviewed, including the main chemical, biological and physical factors that control the degradation of benthic organic matter.
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TL;DR: In this paper, the Gibbs energies of half reactions describing the complete mineralization of a large number of naturally occurring organic compounds were compared to their average nominal carbon oxidation state, and the energy of the half reactions was estimated based on major element (C, H, N, O, P, S) ratios.
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References
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Early oxidation of organic matter in pelagic sediments of the eastern equatorial Atlantic: suboxic diagenesis
Philip N. Froelich,Gary P. Klinkhammer,Michael L. Bender,Nile A. Luedtke,G.R. Heath,Doug Cullen,Paul Dauphin,Doug Hammond,Blayne Hartman,Val Maynard +9 more
TL;DR: Pore water profiles of total CO 2, pH, PO 3−4, NO − 3 plus NO − 2, SO 2− 4, S 2−, Fe 2+ and Mn 2+ have been obtained in cores from pelagic sediments of the eastern equatorial Atlantic under waters of moderate to high productivity as mentioned in this paper.
Book
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An estimate of global primary production in the ocean from satellite radiometer data
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The role of sedimentary organic matter in bacterial sulfate reduction: The G model tested1
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