HR: 11:05h
AN: H12C-03    [Abstracts]
TI: Mechanisms of Non-Fickian Transport
AU: * Scher, H
EM: harvey.scher@weizmann.ac.il
AF: Weizmann Institute of Science, Dept. of Environmental Sciences, Rehovot, 76100, Israel
AU: Emmanuel, S
EM: simon.emmanuel@yale.edu
AF: Yale University, Dept. of Geology and Geophysics, New Haven, CT 06520, United States
AU: Berkowitz, B
EM: brian.berkowitz@weizmann.ac.il
AF: Weizmann Institute of Science, Dept. of Environmental Sciences, Rehovot, 76100, Israel
AB: Non-Fickian transport behavior is due to a broad spectrum of rates limiting the solute movement. There are two generic mechanisms that can generate such a spectrum: the complex flow field of a disordered medium and the mass exchange between a mobile phase and a distribution of immobile states. We derive the basis of incorporating both of these mechanisms into the continuous time random walk (CTRW) framework and systematically study their interaction dynamics as a function of the spectra of advective- diffusive transition times and exchange times, and the relative separation of their respective time domains. Delineating the mechanisms is often subtle and the emphasis in the present study is on explicit physical situations in which these two different types of spectra are distinguishable, so that a more complete characterization of the transport can be obtained (i.e., rather than lumping all the rates together). Experimental data are analyzed from two such systems: (1) tracer transport in a fractured shear zone, and (2) sorbing species transported through a heterogeneous porous domain. In both systems, the data are analyzed within the CTRW framework, and compared also to the standard approach (use of the advection-dispersion equation and first order transfer). The latter does not account for the data while the CTRW framework is found to produce excellent fits and predictions, using a single set of parameters. New numerical techniques are also shown that enhance the stable solution of the nonlocal-in-time transport equation.
DE: 1832 Groundwater transport
DE: 1847 Modeling
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: 2007 Fall Meeting