Collaborative Research: A Systematic Study of solute Transport Influenced by Preferential Flow Paths at the Decimeter and Smaller Scales

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Zheng0003511Recent studies at the Macrodispersion Experiment (MADE) site in Columbus, Mississippi have indicated that the preferential flow paths resulting from aquifer heterogeneities at decimeter (dm) and smaller scales appear to have a dominant effect on plume-scale solute transport. This collaborative research responds to the general lack of studies on the effect of dm-scale heterogeneities on plume-scale solute transport as observed at the MADE site. Our intent is to systematically study the characteristics of solute transport influenced by dm-scale preferential flow paths, and rigorously test the hypothesis that a dual-domain mass transfer approach can provide an effective representation of such characteristics.Four specific elements are integrated into the proposed research. (1) Generate 3-D geologically plausible networks of dm-scale fluvially deposited channels and simulate detailed transport in such systems. (2) Assess the ability of the dual-domain mass transfer model, and possibly other alternative models, to represent the key characteristics of solute transport. (3) Conduct a series of large-diameter column experiments to measure the mass transfer model parameter values under different heterogeneity configurations and flow rates. (4) Conduct tracer tests at the MADE site to obtain the mass transfer model parameter values, using dye-tracing, soil coring and image analysis aimed at providing direct field evidence of preferential flow paths. We will attempt to relate the lithologic characteristics to the mass transfer model parameters obtained from the tracer tests.