> I am starting a project that will deal with chemical equilibrium and I wanted to determine if there is consensus within USGS and USEPA as to which of these models is most appropriate for problems of this nature. I was told that the client wants to do the work with MINTEQ but I am not sure of his rationale. Are there any pitfalls with using MINTEQ over PHREEQC? I think the choice is the matter of preference and capability. Minteq has additional sorption models relative to PHREEQC, triple layer, constant capacitance, langmuir, and freundlich. minteq has a "sweep" option which simplifies calculations in some case, for example, if you want to run the same calculation at multiple pH values. PHREEQC can do the problem, but requires more input (PHREEQC requires consideration of the reactant that fixes the pH, which is probably a good thing). PHREEQC has capabilities for kinetics, 1D-transport, solid-solution, cation exchange, and gas-phase calculations, which I do not think are present in Minteq. PHREEQC has only one sorption model, the diffuse double layer model of Dzombak and Morel, but Freundlich and Langmuir isotherms can be modeled by using some careful (obscure) definitions. PHREEQC has 4 databases that are distributed with the code, phreeqc.dat, wateq4f.dat, minteq.dat, and llnl.dat. phreeqc.dat is a subset of wateq4f.dat, which is essentially equivalent to the database in wateq4f. minteq.dat is nearly equivalent to an older minteq database, but I think there has been a release of minteq with revised thermodynamic data relative to the minteq.dat database that comes with PHREEQC. llnl.dat is derived from the EQ3/6 and is nearly identical with the database for EQ3/6 and Geochemists Workbench. > I have successfully installed a windows version of MINTEQ that was developed by the Swedish. It seems to operate fine. However the US EPA version of MINTEQ is DOS-based and not compatible with Windows XP. PhreeqcI is a Windows interface that works with all versions of Windows from Win95 on. It has screen-driven input for all features of PHREEQC except some of the isotope extensions. > Given what you know please provide opinions about the use of one or both of these programs. Again it is a matter of choice. If the client wants minteq then you may need to use minteq. I think overall, phreeqc has more capabilities and a better interface, although I am not familiar with the Swedish version. You should be able to make most of the calculations of Minteq with PHREEQC, I don't think the reverse is true. Did EPA answer your email? 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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