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Re: PHREEQC




I can't tell what is going on, but my first guess is that you've got too
many phases. Though not stated, the program can only handle about 30
possible reactants in INVERSE_MODELING. However, practically, the limit is
much lower, somewhere between 10 and 20, probably.

If you send me the input file, I'll take a look.

David

David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225


                                                                                                                              
                      James W Ball                                                                                            
                                               To:      rebecca evans <evansre@xxxxxxxxxxxx>                                  
                      03/13/01 09:17 AM        cc:      David L Parkhurst/WRD/USGS/DOI@xxxx                                   
In-Reply-To: <OFE9FAFCD0.7A72646B-ON87256A0E.005D03FC@xxxxxxxx>
                                               Subject: Re: PHREEQC(Document link: David L Parkhurst)                         
                                                                                                                              



Dear Rebecca,
Thanks for your email describing problems you are experiencing with the
phreeqc program. Unfortunately, although you have chosen the appropriate
phreeqc database (wateq4f) based on your list of aqueous components, I am
most likely not the person that can help you the most with your
difficulties. The person I go to with my phreeqc problems is David
Parkhurst, the main author of the phreeqc series of geochemical codes. I am
cc'ing him your attached email in the hope he can help you. (David, can you
help?). Just as an aside, based on your statement of your investigation I'm
curious why you chose inverse modeling rather than just speciation/
solubility calculations.

On another subject, I noticed one of the metals on your list is Cr. Since I
am presently developing a Cr section to the wateq4f model I wonder what
your sources are for thermodynamic data and reactions for Cr?

I wish you success in getting your modeling problems resolved. Please let
me know if you think I can assist you further.
Jim
=====================================
James W Ball
USGS/WRD
3215 Marine Street, Suite E-127
Boulder, CO 80303-1066

jwball@xxxxxxxx
voice:       303-541-3035
fax:           303-447-2505
=====================================


                                                                                                                              
                      rebecca evans                                                                                           
                      <evansre@xxxxxxx         To:      jwball@xxxxxxxx                                                       
                      c.edu>                   cc:                                                                            
In-Reply-To: <OFE9FAFCD0.7A72646B-ON87256A0E.005D03FC@xxxxxxxx>
                                               Subject:                                                                       
                      03/12/2001 06:51                                                                                        
                      PM                                                                                                      
                                                                                                                              
                                                                                                                              



Dear Mr. Ball,
             I am a graduate student working on the Little Miami River in
Ohio. My work
involves studying the association between water quality, water chemistry
and bioaccumulation in benthic algae. My committee suggested I use a
chemical speciation model to predict trace metal dissolution/precipitation
as a lead in to developing hypotheses about what metals I might expect to
accumulate and at what sites in the river.
Here's what I have:
Temp., pH, Oxygen, Total P, Al, Ca, Cd, Cl, Cr, Cu, Fe, K, Mg, Mn, Na, Se,
Si, SO4, and Zn at eleven sites over the length of 105 miles.

             I downloaded PHREEQC along with the WATEQ4f database. I have
been trying
to run inverse modeling (I chose this one because it seemed to best fit
what I am trying to do). The program gets through the solution species and
starts inverse modeling. It does not give me any error messages and does
not appear to be "locked up." The log file is reported as "in use" when I
try to open it in MS Word. However, after as long as 4 hours (when I stop
the program by hitting the "done" icon) all that shows up in the log file
and the output file is the solution species data for each site (currently I
have only two sites entered until I figure out how to operate this
correctly), and the line: "beginning of inverse modeling calcualtions."
             I'm pretty sure the solutions balance and there are no input
errors
because initially I had those problems and the PHREEQC program notified me
with error messages. However, now it seems to be working, I'm just not sure
why I am not getting a series of results in the inverse modeling part.
             My questions are these: 1) Is the program working and just
something I
have to let run for more than four hours? 2) If not, any suggestions? 3)
Would another PHREEQC model be better for the questions I am trying to
answer?
             I appreciate any input you can give me.
Thank You!
Becky Evans









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