Other
Scientific paper
Sep 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995gecoa..59.3707b&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 59, Issue 18, pp.3707-3715
Other
22
Scientific paper
Anaerobic methane oxidation on the Amazon shelf is strongly controlled by dynamic physical sedimentation processes. Rapidly accumulating, physically reworked deltaic sediments characteristic of much of the shelf typically support what appear to be low rates of steady state anaerobic methane oxidation at depths of 5-8 m below the sediment-water interface. Methane oxidation in these cases is responsible for < ~10% of the CO 2 inventory in the oxidation zone and is limited largely by the steady-state diffusive flux of methane into the overlying sulfate reduction zone. In contrast, a large area of the shelf has been extensively eroded, reexposing once deeply buried ( >10 m) methane-charged sediment directly to seawater. In this nonsteady-state situation, methane is a major source of recently produced CO 2 and an important reductant for sulfate. These observations suggest that authigenic sedimentary carbonates derived from anaerobic methane oxidation may sometimes reflect physically enhanced nonsteady-state exposure of methane to sulfate in otherwise biogeochemically unreactive deposits. The concentration profiles of CH 4 , SO 4 = , and CO 2 in the eroded deposit were reproduced by a coupled reaction-transport model. This area of the shelf was reexposed to seawater approximately 5-10 years ago based on the model results and the assumption that the erosion of the deposit occurred as a single event that has now ceased. The necessary second order rate constant for anaerobic methane oxidation was 0.1 mM -1 d -1 .
Aller Robert C.
Blair Neal E.
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