Page 128 - gas transport in porous media

CHAPTER 7

GAS-PHASE DISPERSION IN POROUS MEDIA

MOLLY S. COSTANZA-ROBINSON 1,2 AND MARK L. BRUSSEAU 3,4
1 Program of Environmental Studies, Middlebury College, Middlebury, Vermont 05753
mcostanz@middlebury.edu
2 Department of Chemistry and Biochemistry, Middlebury College, VT, USA
3 Soil, Water and Environmental Science Department, The University of Arizona, Tucson, AZ, USA
4 Hydrology and Water Resources Department, The University of Arizona, Tucson, AZ, USA

7.1 INTRODUCTION

Solute dispersion refers to the spatial spreading of a solute plume over time. The
spreading is essentially a mixing and consequent dilution of the solute plume with
the resident fluid, as depicted in Figure 7.1. Consideration of dispersion is critical to
understanding gas-phase transport in porous media.
Many transport principles that were originally developed to describe behavior in
saturated porous media, and later for unsaturated water flow, can also be readily

A

t 1
t 2
t 3
B
x 1 x 2 x 3
C C C

t t t

Figure 7.1. Spreading of a solute plume from an instantaneous point source. (A)Two-dimensional spatial
“snapshots” (concentration versus x-y coordinates) as a function of time (t). (B) Temporal breakthough
curves (concentration versus time) as a function of distance along axis of flow (x)
121
C. Ho and S. Webb (eds.), Gas Transport in Porous Media, 121–132.
© 2006 Springer.