HR: 0800h
AN: H51F-0433    [Abstracts]
TI: Sub-centimeter scale analysis of dispersion for solute transport through laboratory scale cross-bedded sandstone
AU: * Klise, K A
EM: kaklise@sandia.gov
AF: Geohydrology Department, Sandia National Laboratories, PO Box 5800, MS0735, Albuquerque, NM 87185
AU: Tidwell, V C
EM: vctidwe@sandia.gov
AF: Geohydrology Department, Sandia National Laboratories, PO Box 5800, MS0735, Albuquerque, NM 87185
AU: McKenna, S A
EM: samcken@sandia.gov
AF: Geohydrology Department, Sandia National Laboratories, PO Box 5800, MS0735, Albuquerque, NM 87185
AB: Complex heterogeneity of geologic materials imposes considerable influence on patterns of subsurface flow and solute transport. Understanding such controls are fundamental to developing accurate models for the purpose of design and prediction. Numerous studies point to the failure of Gaussian dispersion to accurately capture flow and transport through heterogeneous porous media. This anomalous, or non-Fickian, dispersion has been attributed to small-scale heterogeneity. This paper tests assumptions of Gaussian based dispersion to predict the behavior of transport through cross-bedded sandstone characterized to the sub-centimeter scale. A laboratory scale slab of Massillon Sandstone exhibiting nested scales of heterogeneity was selected for the research. Permeability and porosity measured to sub-centimeter scale resolution are used to numerically simulate experimental tracer tests. Results suggest that under the assumptions of Gaussian based transport, heterogeneity averaged to the sub-centimeter scale is not adequate for predicting solute transport exhibited by the laboratory experiments. A thorough investigation of potential experimental errors suggests that the failure to fit spatial solute distribution and breakthrough curve characteristics may lie in the inability to capture the connectivity within the cross-bedded sandstone below the sub-centimeter scale. Breakthrough curves show early time arrival and late time recovery that is better captured by a Levy dispersion regime as implemented in one-dimensional Fractional Advection Dispersion Equations. To explore the relationship between the nature of dispersion and the underlying heterogeneity, this study uses estimation procedures that aim to associate tailing of heterogeneity distributions with tailing of solute transport. Results suggest that estimation of heavy-tailed solute transport based on measured permeability, porosity, and visual rock attributes indicate a weaker tailing effect than defined by the Levy dispersion that best fits the experimental solute breakthrough curve. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
DE: 1719 Hydrology
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: Fall Meeting 2005