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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
corresponds to standard water quality for seawater.    I have always
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 Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

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