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
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