RE: Interactive PHREEQC

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

First, I'm guessing that Fe and Al should be ug/L rather than mg/L. Even if
ug/L is correct for these elements, the charge balance of the solution is
not good. The cations are much greater than the anions.

In addition, I think there are errors in llnl.dat. The species AsO3F-- and
HAsO3F- have log K's that appear much too large and actually cause the
program to fail to converge. All of the As or F (whichever is less in
concentration) is tied up in these species, which are 40 orders of
magnitude greater than the other aqueous species of the element. You can
either remove As or F, if they are not important to your investigation, or
redefine the log K's for these species as done below. If you really want to
track it down, you probably need to go back to the literature and find the
thermodynamic data used to generate llnl.dat. I suspect there is a sign
error in the free energy of formation.

> On a related note, is it possible to have more than one masters species?

You can only have one primary master species, but you can have multiple
secondary master species for different redox states of the element.

> I have a few instances where I have 2 or more radionuclides.  Do I
default
to the radionuclide with the greatest solution concentration and treat the
rest as incidental species, or do I do separate determinations for each
radionuclide as if there were no competing radionuclide species?

You can define multiple "elements". You could define C and [13C] as element
names and then define all of the aqueous species for each ( CO2, CO3-2,
HCO3-, etc;  [13C]O2, [13C]O3-2, H[13C]O3-, etc). An element name is either
a single capital letter followed by 0 or more lower case letters or any
alphanumeric string enclosed in square brackets. Additional capabilities
for handling isotopes should be available by the end of the year.

David


TITLE Speciate RGA 004-020
SOLUTION 1  groundwater chemical analysis from Sep 11, 1999
        units   mg/L
        pH      6.02
        pe      2.73
        density 1.0
        temp    15.0
        Ca              90.4
        Mg              70.8
        Na              16.0
        K               44.4
        Fe              1810.0 ug/l  # ????
        Tc              0.0206
        Cl              41.3
        Alkalinity      47.0 as HCO3-
        S(6)            7.8
        F               0.15
        As              0.009
        Cr              1.55
        Ni              0.5
        Al              944.0   ug/L # ????
        Cd              0.022
        Pb              0.757

SOLUTION_SPECIES
 1.0000 H2AsO4- + 1.0000 F-  =  AsO3F-- +1.0000 H2O
        -llnl_gamma           4.0
#        log_k           +40.2451
         log_k           -20


1.0000 H2AsO4- + 1.0000 H+ + 1.0000 F-  =  HAsO3F- +1.0000 H2O
        -llnl_gamma           4.0
#        log_k           +46.1158
         log_k           -20

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