Transport in PHREEQC

[dlevy@xxxxxxxxxxxx (Dave Levy)]

Hi Dr. Parkhurst:

Over the past year or so you have been very helpful in answering questions
regarding some specific questions I have had using PHREEQC to model
geochemical reactions and transport. This model initially used a constant
source term (representing acid tailing water) moving as one-dimensional
advective flow through aquifer material containing native groundwater.  I
would now like to model the same situation, but by incorporating a
decreasing source term. Is it possible to take the input solution (SOLUTION
0), run it for a certain number of shifts, then reduce the concentrations,
say, 33%, run the new SOLUTION  0 for an additional number of shifts,
reduce the concentrations again, and so forth?  I would like the
SELECTED_OUTPUT file to show the final concentrations in the last cell
after a series of these solutions have been run.  I have seen a limited
number of smaller-scale examples of this problem.  I am thinking that the
basic set up for a 20 cell model with exchange and surface adsorption
reactions (just for two solutions here) is as shown below.  I was hoping
you could provide some guidance and possibly take a look at my input file
once I get it setup.  My main concern is getting the SELECTED_OUTPUT and
END statements in the right place so that I know the model is doing what I
want it to do.  Are the keywords in the following example in the right order?

SOLUTION 0  #first inflow solution

SOLUTIONS 1-20

SURFACE 1-20

EXCHANGE 1-20

ADVECTION
	-cells 20
	-shifts (correponding to time for the first SOLUTION 0)

END (needed here or not?)

SOLUTION 0  #second inflow solution

SOLUTIONS 1-20

SURFACE 1-20

EXCHANGE 1-20

ADVECTION
	-cells 20
	-shifts (corresponding to time for the second SOLUTION 0)

SELECTED_OUTPUT

USER_PUNCH

END





-----------------------------------------------------
David B. Levy, Ph.D.
Soil Scientist/Geochemist
Shepherd Miller, Inc.
3801 Automation Way Suite 100
Fort Collins, CO 80525
Phone: 970.223.9600
FAX:   970.223.7171