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Tom Meuzelaar

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Everything posted by Tom Meuzelaar

  1. Hello: You can manually titrate gases into solution using a program such as PHREEQC or The Geochemist's Workbench via reaction path model. This should calculate your dissolved concentrations. Hope this helps, Tom
  2. Hi David: Water activity is the activity of the water phase, it is not the same thing as water vapor fugacity. Would you mind attaching a saved copy of your script so I can take a look at it? Regards, Tom
  3. Hi David: Still not exactly sure what you are trying to do [remainder of this post deleted, follow up with response below]. Hope that helps, Tom
  4. Hi David: GWB calculates water vapor fugacity as well- you can see this under the 'gas fugacities' section in the text output, or under the Gtplot plotting variables. Hope that helps, Tom Meuzelaar RockWare, Inc.
  5. Hello: This isn't necessarily an issue with charge balance. It could be that you've defined a system that is far from equilibrium, and thus has trouble converging. If the pH value is important, I recommend starting with 3.5, so the system initially converges, then sliding the pH (in the Reactants pane) down to 3.1, so that you have a stable chemistry. Hope that helps, Tom Meuzelaar RockWare, Inc.
  6. Hi Jack: When I look at the plot results for your script, it appears that the pH drops to 3.5 after the addition of 1 kg of fluid, correctly mimicking the flush configuration. Do you see something different? Regards, Tom Meuzelaar RockWare, Inc.
  7. Hi Godfrey: The zero values are not allowable- I would start by removing them (or replacing them with n/d notation in GSS). Hope that helps, Tom Meuzelaar RockWare, Inc.
  8. Hi: The time function in React is primarily used for kinetic mineral dissolution and precipitation. Without specifying a kinetic mineral rate law, it doesn't matter what time length you specify, you'll always get the same reaction results. Hope that helps, Tom Meuzelaar RockWare, Inc.
  9. Hi Olivia: We are wondering if a firewall or anti-virus program are temporarily disabling the software that runs your hardware lock. Is it possible to disable your firewall and/or antivirus software to see if that makes a difference? If it does not, can you go to the following address on your browser: http://localhost:1947, and click on the HASP keys menu on the left hand side? Please send the resulting screenshot to my attention via email. Regards, Tom Meuzelaar RockWare, Inc.
  10. Hi: It looks like the low pH is the reason for non-convergence. If you try a slightly higher pH (3.5), the script runs fine. Hope that helps, Tom Meuzelaar RockWare, Inc.
  11. Hi Ken: I'd start by taking a look at polythermal reaction path models in the Reaction Modeling User's Guide. You should be able to view the pH vs. temperature trends in Gtplot. Dealing with variable pressures is going to be a bit trickier, given that the database is compiled for a single confining pressure (1 atm). For most aqueous species and minerals, the equilibrium constant data does not change significantly, but for gases it is a different story altogether, and you may need to make some database modifications. Hope that helps get you started, Tom Meuzelaar RockWare, Inc.
  12. Hello: Yes, I've used the RC_helper.h and RC_helper.cpp source files without too much trouble using Visual Studio. I had to adjust a few settings in the default setup for VS, including: 1. In project settings, remove explicit use of the Unicode character set. 2. Turn off use of precompiled headers However, these settings are specific to Visual Studio, so they may or may not help you. I can tell you that there is nothing wrong with the RC_helper.h and RC_helper.cpp code, and that your problem is probably somewhere in the configuration of the application you are using for code development. Unfortunately, my response time will be much slower after this, as I am about to step out for a 4-day holiday weekend. Regards, Tom Meuzelaar RockWare, Inc.
  13. Hello: I recommend checking your syntax- as the error messages suggest,this is likely cause by missing a semicolon somewhere. If this occurs in one line of code, all of the other lines of code can become uninterpretable. I hope that helps, Tom Meuzelaar RockWare,Inc.
  14. Hi Ruth: This should work fine- just be sure to: constrain the oxygen concentration in the system specify a pH convert your total As concentration to the arsenic basis species GWB will speciate all of your arsenic among all dissolved arsenic species in the thermo database according to their equilibrium constants. Let me know how I can be of further help. Regards, Tom Meuzelaar RockWare, Inc.
  15. Dear Christoph: The reason for this is that the temperature dependence of the rate constant is defined as a function of the activation energy (Ea) and pre-exponential factor (A) as follows: If you have a kinetic rate law that includes both a rate constant and activation energy, you might consider using the Custom Rate Law features in GWB. Hope that helps, Tom Meuzelaar RockWare, Inc.
  16. Hi Emma: React can work with waters that have negative pH (see attached script), but I don't think it will take a negative pH as input. Instead, use the equivalent proton activity to constrain your model. I hope that helps. Tom Meuzelaar RockWare, Inc. negative_pH.rea
  17. Hello- I have a little PHREEQC experience, but you are better off going to the PHREEQC support pages on the USGS website.

  18. Hello- I have a little PHREEQC experience, but you are better off going to the PHREEQC support pages on the USGS website.

  19. Hi Ross: Glad you were able to get it working- yes, usually the problem for has been a missing quote here, or an extra parenthesis there.... The devil is in the details. I appreciate you sharing with the User's Group. Regards, Tom Meuzelaar RockWare, Inc.
  20. Hi Ross: Yes, your rate law evaluates to zero in the output file. I can't spot the issue right off- troubleshooting rate law scripts can tedious and time-consuming. What I recommend is that you simplify the script and first test your neutral, acid and base rates individually. Then put them together into your combined rate law. Hope that helps, Tom Meuzelaar RockWare, Inc.
  21. Hi Adam: You can do this using React, a simple mixing model, and the Pickup command. First add your acid groundwater to the React Basis. Speciate this water, and use the Config - Pickup - Reactants command to load the speciated water into the Reactants tab. Next load your surface water into the Basis tab. You now have a model simulating gradual titration of acidic groundwater into surface water. You'll run into a problem due to the fact that your surface water does not have all the components of your acid groundwater (Br-, Al, Fe, Mn). Remedy this by either excluding these components from your acid groundwater analysis, or by adding acceptably low concentrations for these components to your surface water in the Basis. I hope that helps, Tom Meuzelaar RockWare, Inc.
  22. Hi Ross: I've attached a working sample script.... Regards, Tom qtz_kinetic_test.rea
  23. Hi Ross: It turns our that the rate law script, as written in the v8 Reaction Modeling user's guide (page 56), reflects command line syntax. The actual code for the direct script editor looks exactly like the code you would put in a .bas file- you only need the code in between the brackets- not the 'kinetic Albite rate_law = { }' part. I hope that makes sense... We'll update the User's Guide to be a little more clear. Regards, Tom Meuzelaar RockWare, Inc.
  24. Hi Ross: I simplified the script quite a bit, and am still getting a syntax error in line 1, even though the format appears to be correct. I'll need to check with the developers to see if I'm doing something wrong here. However, there's a simple work-around. Save the file in notepad with a .bas extension, and load it in as a Rate law script file. Let me know if that resolves the issue. Regards, Tom Meuzelaar RockWare, Inc.
  25. Hi Ross: Sure- in X2t, choose Config - Second Reaction Interval. Then in Config - Wells, add a well, and you'll notice that you can specify two injection rates. Set the first one to be your injection (positive rate) and the second to be your recovery (negative rate). Be sure to set the Time for both intervals in the Initial pane. Hope that helps, Tom Meuzelaar RockWare, Inc.
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