CRPC-TR99798						September 1999

Title: Dispersion-Induced Chromatographic Waves

Authors: Steven L. Bryant, Clint Dawson, and Cornelius J. van Duijn

Submitted November 1999

Abstract:
     Motivated by field and laboratory observations of unusual wave
propagation, we investigate the behavior of simple model problems
involving transport with competitive adsorption of H+ and a metal cation.
In the absence of diffusion/dispersion, the model problem yields two
shocks with the velocities expected from classical theory.  In the
presence of diffusion/dispersion, the solution exhibits an additional
feature, a pulse of metal ion concentration that moves rapidly and
independently of the metal ion shock.  This 'fast wave' is associated with
the pH shock in the simplest model problem studied here.  Theoretical
analysis of this problem yields a jump condition which numerical
experiments confirm.  Along with diffusion/dispersion, proton
sorption/desorption appears to be prerequisite for this phenomenon.  This
extension of classical chromatography theory may explain several field and
laboratory observations.  One practical implication of this finding is the
importance of accurate handling of diffusion and dispersion in numerical
simulation of reactive transport problems.  Another is that estimates of
species migration based on simple theory, such as retardation factors, may
fail to capture important features of the actual behavior.

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Steven L. Bryant
sbryant@ticam.utexas.edu
Center for Subsurface Modeling
The University of Texas

Clint Dawson
cdawson@ticam.utexas.edu
Center for Subsurface Modeling
The University of Texas

Cornelius J. van Duijn
CWI
Amsterdam, The Netherlands