A discussion forum for STANMOD users. STudio of ANalytical MODels is a software package for evaluating solute transport in porous media using analytical solutions of the convection-dispersion solute transport equation.

wuhuayong
Posts: 10
Joined: Mon Dec 14, 2009 9:10 am

Hi all,
Transport of a partitioning gas tracer into and out of homogenous soil columns can be described by a single-region model.In this model, the entire gas phase is assumed to be mobile and the water immobile. Partitioning of tracers between the gas and immobile water phase is assumed to be linear and described by a first-order rate equation, while tracer interaction with the solid phase is assumed to be negligible.
I am using CXTFIT to simulate such single-region model. But I have a question.The question is how to defines the dimensionless parameters(P,R,Beta,omega) ?
Thank you a lot.

ntoride
Posts: 74
Joined: Fri May 21, 2004 12:50 pm
Location: Japan
wuhuayong:
It would be interesting to try MIM to the gas transport. Please look at the CXTFIT manual(p.16-18). Nondimensional parameters are defined in Table 3.1. Also refer to van Genuchten and Wagnet (1989, SSSAJ, 1303-1310) . If any further questions, please do not hesitate to ask me.
Nobuo

wuhuayong
Posts: 10
Joined: Mon Dec 14, 2009 9:10 am
Dear Nobuo,
Thank you for suggestion. I already have the manual on hand. But I sitll have some doubts.
In MIM, Beta is defined as (¦?m+f*¦?*Kd)/(¦?+¦?*Kd). As we know, f=¦?m/¦?. So can I make a conclusion that Beta=f?
Thanks a lot.
wuhuayong

ntoride
Posts: 74
Joined: Fri May 21, 2004 12:50 pm
Location: Japan
wuhuayong:
Sorry for my late reply. For nonreactive solutes, Kd is equal to zero. In this case, beta is the fraction of the mobile phase, theta_m/theta. I think this is a possible MIM assumption for the gas transport. Nobuo

wuhuayong
Posts: 10
Joined: Mon Dec 14, 2009 9:10 am
Dear Nobuo,
I think maybe it's a possible MIM model.I still have a doubt. For nonrective tracer, R=1. But how to character the retardation by gas tracers partitioning into water.
I am sorry to have so much doubts. Thanks a lot for your patience.

rvang
Posts: 46
Joined: Wed Apr 24, 2002 7:22 pm
Location: USA
Contact:
Wuhayong:

Assume one-site kinetic partioning from the gas phase into the liquid phase. Use f=0 (no sorptio in gas phase), and interpret k (or Kd) as the partionining coefficient between the gas and liquid phases.

Good luck. --Rien van G.