Re: Equil_phases

["David L Parkhurst" <dlpark@xxxxxxxx>]

> I have computed a value (EQUILIBRIUM_PHASES 1;  Gibbsite  0 10)
for a single sample but, would like to know if there a way to repeat
this command for each sample (in the SOL_SPREAD)?  Or do I
have to SAVE each 'initial solution 1-20'?

It is possible to estimate the Al concentration that would give equilibrium
with gibbsite within the SOLUTION_SPREAD definition. However, it is not
identical to the calculation you performed for solution 1. By adding a
column for Al and a subheading of "Gibbsite", the program will adjust the
aluminum concentration until the saturation index for gibbsite for the
solution is 0.0. Note that the pH and all other concentrations are not
affected in this calculation. When you use equilibrium_phases, a different
calculation is performed: Al(OH)3 is added to the solution until the
saturation index for gibbsite is 0.0. Thus, OH is added in addition to Al
and the pH will consequently change. The first method with SOLUTION_SPREAD
is probably what you want to do, keeping everything in the solution
unchanged, except estimating an aluminum concentration.

Note that even using gibbsite in solution_spread, and including the
equilibrium_phases calculation, the reaction calculation with equilibrium
phases dissolves some more gibbsite. This is because of redox reactions
with nitrogen. The reaction calculation forces redox equilibrium, which
causes adjustments among N(-3), N(0), and N(5). These reactions affect the
pH, which in turn causes gibbsite to adjust.

David

Not sure the units are correct in this file, the tabs didn't come through
in the email.

(See attached file: Phrqc3.pqi)



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

Attachment: Phrqc3.pqi
Description: Binary data