Manganese geochemistry in Galveston Bay sediment.

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dc.acquisition-srcen_US
dc.call-noQE571.T3 1987 GBAYen_US
dc.contract-noen_US
dc.contributor.authorTaylor, R.J.en_US
dc.contributor.otheren_US
dc.date.accessioned2010-02-15T16:57:10Z
dc.date.available2010-02-15T16:57:10Z
dc.date.issued1987en_US
dc.degreeen_US
dc.description258 p., Dissertationen_US
dc.description-otheren_US
dc.description.abstractThe sediment geochemistry of Mn at a site in Galveston Bay, Texas, was investigated through a three-fold approach. A field study demonstrated that despite the coarse, quartz-rich nature of the bottom sediments, Mn was extensively remobilized within the sediment and that a large fraction of the incoming Mn flux was returned to the water column (=80-90%, relative to overlying suspended matter). Laboratory experiments showed that Mn(II) adsorption onto natural sediment follows a nonlinear Freundlich isotherm, and is dependent upon the relative proportions of quartz sand and fine-grained aluminosilicate material. Manganese(II) oxidation in the presence of Galveston Bay sediment is also dependent upon grain size distribution, follows Michaelis-Menten-type kinetics with respect to dissolved O2, and is independent of dissolved Mn(II) within the concentration range 20-300 microM. Below 20 microM, nonlinear adsorption effects prevent unambiguous interpretation of oxidation behavior. Sediment incubation experiments showed that production of dissolved Mn(II) through reduction of Mn oxides occurs shortly after isolation of sediment from the atmosphere, and that it is independent of Mn oxide concentration over a wide concentration range. These experiments also resulted in the first laboratory determination of the Mn(II) removal rate constant for anoxic sediments. Numerical modeling of dissolved and solid phase Mn, using reaction rate constants determined in the laboratory investigation, failed to predict profiles and fluxes observed in the field when the only mechanism for loss was molecular diffusion. Manipulation of physical and reaction parameters in the model demonstrated that the high Mn(II) oxidation rate was responsible for almost quantitative Mn retention, even though the O2-containing layer was only 2-3 millimeters in thickness. This observation and absence of worm tubes at the collection site indicate that export of Mn is accomplished through some process other than molecular diffusion or sediment irrigation by biota. Additional modeling indicated that the Mn depletion observed in sediment cores may result from either episodic erosive or anoxic events, or from continous resuspension of surficial sediment. Finally, modelling of the effect of an impermeable object, located at the sediment:water interface, indicates that in nearshore areas where the oxidized surface layer is only millimeters thick, distributions and fluxes of both O2 and dissolved Mn(II) may be affected locally by objects with diameters on the order of one millimeter.en_US
dc.description.urihttp://gbic.tamug.edu/request.htmen_US
dc.geo-codeGalveston Bayen_US
dc.historyen_US
dc.identifier.urihttp://hdl.handle.net/1969.3/20356
dc.latitudeen_US
dc.locationGBIC Collectionen_US
dc.longitudeen_US
dc.notesen_US
dc.placeCollege Station, Texasen_US
dc.publisherTexas A&M University.en_US
dc.relation.ispartofseries2564.00en_US
dc.relation.urien_US
dc.scaleen_US
dc.seriesen_US
dc.subjectmodelsen_US
dc.subjectmanganeseen_US
dc.subjectgeochemistryen_US
dc.subjectsediment analysisen_US
dc.titleManganese geochemistry in Galveston Bay sediment.en_US
dc.typeBooken_US
dc.universityen_US
dc.vol-issueen_US

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