SS2.02 Biogeochemical Process at the Sediment-Water Interfaces
Date: Tuesday, June 11, 2002
Time: 12:00:00 PM
Location: Carson B
 
van LithY, Department of Geochemistry, Univ. Utrecht, Budapestlaan 4, 3508 TA Utrecht, Netherlands, y.vanlith@geo.uu.nl
Van Cappellen, P, , Department of Geochemistry, Utrecht, Netherlands, pvc@geo.uu.nl
 
MANGANESE AND IRON REDUCTION IN TIDAL SEDIMENTS OF THE SCHELDT ESTUARY, THE NETHERLANDS
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Manganese and iron reduction in tidal sediments is coupled to the cycling of carbon, sulfur, and phosphorus. Reduction of manganese and iron oxides affect the ecosystem through their association with trace metals. We attempt to quantify microbial manganese and iron reduction compared to chemical reduction, by investigating the coupling of manganese and iron reduction to the oxidation of organic matter. Sediment profiles in the Scheldt Estuary indicate manganese and iron reduction just below the sediment water interface. Enrichment cultures isolated from the sediment demonstrate that manganese reduction rates increase when a more diverse substrate mixture is offered, indicating the coupling of oxide reduction to organic matter oxidation. Bacterial manganese reduction is observed in the first 2-3 days of the incubation, coinciding with adsorption of the liberated Mn(II) to the manganese oxide. Bacterial iron reduction continues through the first 15 days and Fe(II) adsorbs to the iron oxide. Cultures growing on both manganese and iron oxides demonstrate that bacteria preferentially use iron oxide and that only little manganese reduction occurs after 15 days, chemical or microbial.