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Pfeifer, Kerstin; Hensen, Christian; Adler, M; Wenzhöfer, Frank; Weber, Bettina; Schulz, Horst D (2002): Chemistry of sediment profile GeoB4906. PANGAEA,, Supplement to: Pfeifer, K et al. (2002): Modeling of subsurface calcite dissolution - including the respiration and re-oxidation processes of marine sediments in the region of equatorial upwelling off Gabon. Geochimica et Cosmochimica Acta, 66(24), 4247-4259,

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Mineralization of organic matter and the subsequent dissolution of calcite were simulated for surface sediments of the upper continental slope off Gabon by using microsensors to measure O2, pH, pCO2 and Ca2+ (in situ), pore-water concentration profiles of NO3-, NH4+, Fe2+, and Mn2+ and SO42- (ex situ), as well as sulfate reduction rates derived from incubation experiments. The transport and reaction model CoTReM was used to simulate the degradation of organic matter by O2, [NO3]-, Fe(OH)3 and [SO4]2-, reoxidation reactions involving Fe2+ and Mn2+, and precipitation of FeS. Model application revealed an overall rate of organic matter mineralization amounting to 50 µmol C cm**-2 yr**-1, of which 77% were due to O2, 17% to [NO3]- and 3% to Fe(OH)3 and 3% to [SO4]2-. The best fit for the pH profile was achieved by adapting three different dissolution rate constants of calcite ranging between 0.01 and 0.5% d-1 and accounting for different calcite phases in the sediment. A reaction order of 4.5 was assumed in the kinetic rate law. A CaCO3 flux to the sediment was estimated to occur at a rate of 42 g m**-2 yr**-1 in the area of equatorial upwelling. The model predicts a redissolution flux of calcite amounting to 36 g m**-2 yr**-1, thus indicating that ~90% of the calcite flux to the sediment is redissolved.
Related to:
Pfeifer, Kerstin (2003): Auswirkungen frühdiagenetischer Prozesse auf Calcit- und Barytgehalten in marinen Oberflächensedimenten: Modellierung von Lösung und Erhaltung. Berichte aus dem Fachbereich Geowissenschaften der Universität Bremen, 208, 110 pp, urn:nbn:de:gbv:46-ep000103296
Median Latitude: -0.687778 * Median Longitude: 8.380556 * South-bound Latitude: -0.690000 * West-bound Longitude: 8.378333 * North-bound Latitude: -0.686667 * East-bound Longitude: 8.381667
Date/Time Start: 1998-03-02T05:35:00 * Date/Time End: 1998-03-03T14:49:00
GeoB4906-4 * Latitude: -0.690000 * Longitude: 8.378333 * Date/Time: 1998-03-02T05:35:00 * Elevation: -1272.0 m * Recovery: 0.37 m * Location: off Gabun * Campaign: M41/1 * Basis: Meteor (1986) * Device: MultiCorer (MUC) * Comment: 8 big and 4 small tubes
GeoB4906-6 * Latitude Start: -0.686667 * Longitude Start: 8.381667 * Latitude End: -0.686667 * Longitude End: 8.381667 * Date/Time Start: 1998-03-02T07:15:00 * Date/Time End: 1998-03-03T14:49:00 * Elevation: -1252.0 m * Location: off Gabun * Campaign: M41/1 * Basis: Meteor (1986) * Device: PROFILUR Lander (PROFILUR)
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