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: 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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