David-- Thank you, I appreciate your taking time to answer my questions. A final one (hopefully) -- QUESTION: I appreciate the role of kinetics. However, assuming that kinetics are not an issue, how can I best apply PHREEQC to determine, at equlibirum, what remains in solution and what (eventually) precipitates - for a given a water quality? Thank you, Mike ------------------------- Mickley & Associates 752 Gapter Road Boulder, Colorado 80303 303-499-3133 fax 303-499-5305 www.mickleyassoc.com ----- Original Message ----- From: "David L Parkhurst" <dlpark@xxxxxxxx> To: "Mike Mickley" <michael@xxxxxxxxxxxxxxxx> Sent: Monday, August 18, 2003 8:18 AM Subject: Re: trouble downloading PHREEQC for Windows > > > > > QUESTION 1: would you recommend software to use at higher salinities? > EQ3/6 or something else? > > You need a program that includes the Pitzer formulation for activities to > run at higher ionic strengths. EQ3/6, Geochemists Workbench, and TEQUIL > (though I have never successfully downloaded this code) include or are > based on the Pitzer formulation. Note that as far as I know, the Pitzer > formulation does not include any redox reactions, aluminum, or silica. > > > Example 1 of PHREEQC determines the speciation of seawater. The data > input > corresponds to standard water quality for seawater. I have always > assumed > that this 'standard' WQ for seawater refers to the common elements in their > dissolved state. In this instance calcium at 412.3 ppm would be assumed to > be nearly all in ionic form. Yet the results of the simulation suggest > that about 10% of the calcium is present as CaSO4. While nucleation of > CaSO4 can be such that initially it is dissolved I would assume that here > CaSO4 implies solids that are precipitated. > > > QUESTION 2: Is this correct? OR am I missing something? > > You are missing something. The CaSO4 in the distribution of species is a > dissolved ion pair or complex. All species listed in the distribution of > species are dissolved and concentrations defined in SOLUTION refer to total > dissolved concentrations (free ion + complexes). Saturation indices show > the saturation state of the solution relative to minerals. Mineral > equilibria are defined with EQUILIBRIUM_PHASES; KINETICS can be used to > define kinetic reaction of minerals. > > 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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