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Research Interests: My hydrologic work is in the area of unsaturated flow and transport in soils and rocks. Specific research interests include scaling of unsaturated hydraulic phenomena (Fig. 1), fast flow in unsaturated fractured rocks, film flow, unsaturated hydraulics of gravels and rock deposits, and infiltration flow path distributions in rocks. My geochemistry interests are in transport controls on reactions in soils and rocks, at the µm to m scales. Systems studied have diffusion-limited reaction rates, with intragranular- to column-scale transport controlling local equilibration times. This work relies heavily on synchrotron-based methods of x-ray fluorescence microprobe and micro x-ray absorption spectroscopy (Fig. 2). . Fig. 1. Approximate boundaries between different flow regimes in fractured rocks, for (1) unsaturated matrix flow, (2) film flow over effectively saturated rock matrix, and (3) saturated fracture flow. [DOE-BES]
Fig. 2. Chromium diffusion and reduction within soil aggregates. The spatial distribution of Cr in contaminated soils can be very heterogeneous at the soil aggregate scale (mm to cm), because the mobile Cr(VI) may enter primarily through a network of preferential flow paths, then diffuse into the less accessible regions. Diffusion-limited Cr(VI) transport within soil aggregates permits very localized precipitation of Cr(III) in microsites where the concentrations of reductants are sustained at high levels. [DOE-BES, DOE-NABIR] |
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