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Type Curves to Determine the Relative Importance of Advection and Dispersion for Solute and Vapor Transport
Author(s) -
Garges John A.,
Baehr Arthur L.
Publication year - 1998
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1998.tb02102.x
Subject(s) - péclet number , advection , dimensionless quantity , diffusion , dispersion (optics) , flux (metallurgy) , mass flux , mechanics , mass transfer , molecular diffusion , thermodynamics , convection–diffusion equation , chemistry , physics , optics , metric (unit) , operations management , organic chemistry , economics
The relative importance of advection and dispersion for both solute and vapor transport can be determined from type curves for concentration, flux, or cumulative flux. The dimensionless form of the type curves provides a means to directly evaluate the importance of mass transport by advection relative to that of mass transport by diffusion and dispersion. Type curves based on an analytical solution to the advection‐dispersion equation are plotted in terms of dimensionless time and Peclet number. Flux and cumulative flux type curves provide additional rationale for transport regime determination in addition to the traditional concentration type curves. The extension of type curves to include vapor transport with phase partitioning in the unsaturated zone is a new development. Type curves for negative Peclet numbers also are presented. A negative Peclet number characterizes a problem in which the direction of flow is toward the contamination source, and thereby diffusion and advection can act in opposite directions. Examples are the diffusion of solutes away from the downgradient edge of a pump‐and‐treat capture zone, the upward diffusion of vapors through the unsaturated zone with recharge, and the diffusion of solutes through a low hydraulic conductivity cutoff wall with an inward advective gradient.