HR: 1340h
AN: H33E-1428    [Abstracts]
TI: Potential Scale Dependence of Effective Matrix Diffusion Coefficient:Evidence and Preliminary Interpretation
AU: * Liu, H
EM: hhliu@lbl.gov
AF: LBNL, MS 90-1116, Berkeley, CA 94720
AU: Zhang, Y
EM: YQZhang@lbl.gov
AF: LBNL, MS 90-1116, Berkeley, CA 94720
AU: Zhou, Q
EM: QLzhou@lbl.gov
AF: LBNL, MS 90-1116, Berkeley, CA 94720
AU: Molz, F
EM: fredi@clemson.edu
AF: Clemson University, PO Box 340919 , Clemson, SC 29634
AB: Owing to the orders-of-magnitude slower flow velocity in the matrix and significantly larger matrix porosity (compared to fractures), matrix diffusion can significantly retard and dilute solute transport process in fractured rock.Therefore, this phenomenon is important for analyzing a variety of problems, including geological disposal of nuclear waste. Matrix diffusion coefficient values measured from small rock samples in the laboratory are generally used for modeling field-scale solute transport in fractured rock. However, by compiling results from a number of field tracer tests corresponding to different geological settings, this study demonstrates that the effective matrix diffusion coefficient at field scale is generally larger than that at lab scale and tends to increase with testing scale. Preliminary interpretations of this observation are investigated by performing numerical experiments for solute transport in flow paths having geometries consistent with percolation theories and characterized by local flow loops formed mainly by sub-fractures. The flow-path geometries under consideration could result in scale-dependent behavior of the effective matrix diffusion coefficient, with large values being observed at intermediate to large travel distances. Ignoring such values would to systematically under-estimating travel times in fractured rock environments.
DE: 1800 HYDROLOGY
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1859 Rocks: physical properties
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: Fall Meeting 2005