Gas Phase Transport Principal Sources: VLEACH, A One-Dimensional Finite Difference Vadose Zone Leaching Model, Version 2.2 – 1997. United States Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, Subsurface Protection and Remediation Division, Ada, Oklahoma. Šimůnek, J., M. Šejna, and M.T. van Genuchten. 1998. The HYDRUS-1D software package for simulating the one-dimensional movement of water, heat, and multiple solutes in variably- saturated media. Version 2.0, IGWMC - TPS - 70, International Ground Water Modeling Center, Colorado School of Mines, Golden, Colorado, 202pp., 1998.
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Gas Phase Transport Principal Sources: VLEACH, A One-Dimensional Finite Difference Vadose Zone Leaching Model, Version 2.2 – 1997. United States Environmental.
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Gas Phase Transport
Principal Sources:
VLEACH, A One-Dimensional Finite Difference Vadose Zone Leaching Model, Version 2.2 – 1997. United States Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, Subsurface Protection and Remediation Division, Ada, Oklahoma.
Šimůnek, J., M. Šejna, and M.T. van Genuchten. 1998. The HYDRUS-1D software package for simulating the one-dimensional movement of water, heat, and multiple solutes in variably-saturated media. Version 2.0, IGWMC - TPS - 70, International Ground Water Modeling Center, Colorado School of Mines, Golden, Colorado, 202pp., 1998.
Effective Diffusion
• Tortuosity (T = Lpath/L) and percolation (2D)
3/4
2
0a
a
D
D
dx
dCDJ
C
xJD
0
0.1
0.2
0.3
0.4
0.5
0 0.1 0.2 0.3 0.4 0.5Volumetric Air Content
D/D
o
Maxwell (1873)
Buckingham (1904)
Penman (1940)
Marshall (1959)
Millington (1959)
Wesseling (1962)
Currie (1965)
WLR(Marshall):Moldrup et al (2000)
Total Mass
• At Equilibrium:
Henry’s Law
• Dimensionless:
• Common:
wHg CKC
atm m3 mol-1
VLEACH
• VLEACH simulates vertical transport by advection in the liquid phase and by gaseous diffusion in the vapor phase
VLEACH
• VLEACH describes the movement of solutes within and between three different phases:– solute dissolved in
water– gas in the vapor phase– adsorbed compound in
the solid phase • Equilibration between
phases based on distribution coefficients
• Processes are conceptualized as occurring in a number of distinct, user-defined polygons that are vertically divided into a series of user-defined cells