1- When I vary the kinetics with PHAST (ie vary qm and log_k in the '.chem' file) by several orders of magnitude, there is no change in benzene concentrations. The log K for the reaction Benzene = Benzene should be 0. 2- I am comparing the results with MIN3P, and the concentrations for PHAST are a little bit higher, even with kinetics shut off (k = 0). The only way I have been able to get closer to a match is by decreasing the input concentrations of benzene (I have included a graph of this problem where for all simulations k = 0). Any idea why this might be assuming i'm entering the same concentrations for both programs? If conservative chloride matches then so should conservative Benzene (qm = 0). I ran this case and benzene and chloride are identical. I assume MIN3P also gives the same result for conservative Benzene. So the difference you are plotting must be related to kinetics and I don't know the explanation. Could the boundary conditions be different? Perhaps MIN3P fixes the oxygen concentration at the boundary, whereas PHAST does not. That would allow MIN3P to degrade more Benzene. I think PHAST is giving the correct result for the problem definition, but it is hard to check. One thing you can do is to refine the grid on both programs to determine whether the results change. I reran phast with twice as many nodes in each direction and half the time step. The results were nearly identical. Peak chloride concentration increased from .000925 to .000935. Peak benzene concentration increased from .000858 to .000869. The simulation looks ok to me. Benzene is slightly less than chloride because of degradation. Things may look similar with different rates because you run out of oxygen. Oxygen is completely depleted within the benzene plume. David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225 Project web page: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled
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