HR: 1340h
AN: H23D-1616    [Abstracts]
TI: Precipitation Of Iron Minerals In Porous Media
AU: * Grover, D
EM: groverd@onid.orst.edu
AF: Department of Environmental Science, Oregon State University, Corvallis, OR 97330,
AU: Baham, J E
EM: John.Baham@oregonstate.edu
AF: Department of Environmental Science, Oregon State University, Corvallis, OR 97330,
AU: Baham, J E
EM: John.Baham@oregonstate.edu
AF: Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97330,
AU: Dragila, M I
EM: maria.dragila@oregonstate.edu
AF: Department of Environmental Science, Oregon State University, Corvallis, OR 97330,
AU: Dragila, M I
EM: maria.dragila@oregonstate.edu
AF: Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97330,
AB: Formation of soil redoximorphic features, such as mottles, concretions and placic horizons is governed by Fe (II) and oxygen transport in porous media. We have conducted column experiments with four grades of silica sand that were placed vertically in the reduced saturated soil. Two sets of iron bands appeared within one week. Red oxidized bands (ferrihydrite and/or possibly lepidocrocite) were formed at the upper extent of the capillary fringe. Whereas, black bands (magnetite and/or green rust) were formed below the oxidized iron bands. These bands were transformed to the red bands as the experiment progressed. We propose a conceptual mechanistic framework for abiotic band formation and have developed a numerical model that incorporates the relevant factors contributing to the abiotic genesis of iron bands. This study reveals that abiotic iron oxide formation in unsaturated media is mainly a diffusion controlled process. The position of iron oxide bands is regulated by the diffusion rates of Fe (II) (aq) and Oxygen (g); thus elucidating the role of air-water and water-mineral interfacial properties, and diffusion gradients on iron transformations in natural systems. Our results suggest that the formation of Fe (III) oxide cemented bands in unsaturated hydrological systems is a rapid process occurring on a time scale relevant to human activity.
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0471 Oxidation/reduction reactions (4851)
DE: 1847 Modeling
DE: 1865 Soils (0486)
SC: Hydrology [H]
MN: 2007 Fall Meeting