Tom Meuzelaar

Hi Christoph: The actual amount of Calcite dissolved is listed under the heading "Minerals in system", not "Basis Components". In GWB there is a distinction between components, which are mathematical entities and can be negative, and actual minerals and dissolved species, which are physical entities and cannot be negative. This is detailed in Craig Bethke's Geochemical and Biogeochemical Reaction Modeling, Chapter 3. I hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Kelvin: I'm not sure why the sharp boundary exists at the temperature interval you give; it's difficult to troubleshoot given the large number of components in the diagram. The trouble is that you have 7 additional species (all speciating) in addition to your diagram species and axes, rendering the diagram nearly useless. When working with that many components, it's a better idea to move to speciation and reaction path models. Try building this system in React, and then sliding your pH and Eh values to understand the behavior of your system better. Regards, Tom Meuzelaar RockWare, Inc.

Hi Kelvin: Just look in the thermodynamic database that loads when you load one of the modules- the default database is thermo.dat (the Lawrence Livermore National Lab database). To open the database, in any module, choose the Run - View - ..\thermo.dat. Have a look at the Appendix entitled Thermo Databases in the GWB Reference Manual to learn more about how the solubility data are defined over the temperature interval of the database. Hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Kelvin: Turn on the extrapolate setting if there are aqueous species, minerals or gases of interest in your model that do not have log K values defined in the temperature range you are working in. Hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Kelvin: When you originally load the script, React asks you how you would like charge balance set. If you choose to not balance your water, simply select the 'balance off' option under the unit selector to the right of the HCO3- entry. This means that you are running your script with a slightly unbalanced water. Whether or not you choose to charge balance is at your discretion. Regards, Tom

Hi Kelvin: I'm not sure what you changed in your model. Can you attach the new script that is causing the problem? Regards, Tom

Dear Kelvin: In your React script after initial speciation, your Eh and pH are allowed to vary while supersaturated phases are precipitating, whereas they are fixed on the activity diagram. If you add a fixed Eh and pH to your model (see attached), they put you in the correct stability field.

Hi Kelvin: Can you attach your React and Act2 scripts? Regards, Tom Meuzelaar RockWare, Inc.

ok, the fact that you cannot patch has me worried that your installation has somehow become corrupted. Let's try the following: 1. Uninstall GWB from your computer 2. Send me an email- I will email back a link for the full GWB 8.0.10 installation executable (so that you don't have to patch) 3. Reinstall. Let's see if that takes care of the issue. Regards, Tom

Hi Nikolay: Sorry you are getting frustrated. I have your GSS file, and have tried both changing symbols and units, and saving thereafter, but I cannot replicate the crash. First item to consider, have you patched to the latest version of GSS (8.0.10)? If I can replicate it, we can probably fix it... Regards, Tom

Hi Marty: You're currently limited to one sample. With not too much work, you can plot consecutive samples in Gtplot and port the data directly from Gtplot to Excel using the Edit - Copy As - Spreadsheet option in Gtplot, followed up by pasting in Excel. This way you can rapidly build a datasheet for multiple samples, and then plot in Excel. Hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Kelvin: 1. The answer as to whether or not the diagram is the 'correct' diagram depends on your modeling objectives- it is the diagram produced based on the data you put into Act2. However, it sounds like you may want to look further into the sources behind the ferric iron and ferric chloride solubility data in the various thermodynamic databases. 2. You could do this either in SpecE8 or React. In SpecE8 you'd be calculating aqueous speciation at fixed Eh and ph. In React, you could slide either the pH or Eh across a range of values. Hope that helps, Tom

Hi Kelvin: No worries about being a new user- we have many people that are just learning, and the rest of us were all at that place at one point in time or another. Unfortunately, I still have no idea what you are asking in your second question. Can you repeat the entire question for me? Regards, Tom

More specifically, what I am saying is that Analcime can only precipitate as fast as the dissolving glass can provide the species it needs. By the way, there are options in the built-in rate law for the affects that the saturation state of one mineral has on the dissolution/precipitation rate of another. Have a look at section 4.2.3 'Cross-affinity rate laws' in the GWB Reaction Modeling Guide. You might also want to take a look at rate laws that incorporate the effects of promoting and inhibiting species. Hope that helps, Tom

To get the program to calculate pH, you'll need something to constrain the proton- that is, add H+ to your basis, and swap a component that can constrain pH. Frequently modelers will swap in something like CO2 gas fugacity or a mineral to accomplish this. Regarding the precipitates, yes, GWB can calculate which are likely to form. You don't need to define them initially in the Basis pane. Simply define your water composition in the React module and it will precipitate those supersaturated phases which are thermodynamically most likely. Hope that helps, Tom Meuzelaar RockWare, Inc.

Denis: Let me put it another way- Analcime never becomes supersaturated (plot Q/K for Analcime in Gtplot). The reason for this is that the kinetic rate you've provided for Analcime exceeds your glass dissolution rate. Thus, the rate of supply of aqueous components needed for Analcime to precipitate is slower than the rate you've given for the Analcime precipitation itself. You can prove this to yourself by simply removing the kinetic Analcime entry from the Reactants tab. The script runs to completion just fine, and the final plot you get is the same as under your kinetic configuration. Hope that helps, Tom

Hello: There are likely a couple of issue with your script, however, it would be helpful if you could attach a copy of the exact script so we are comparing apples to apples: 1) There are few lithium aqueous species in the default database 2) You'll need to add additional components to your model if you wish to constrain pH and see some of the dissolved boron species 3) In the main input pane, you'll only see what are called 'basis species', which are essentially the building blocks of the thermodynamic database. Other aqueous species and minerals can be added to your input file via swapping. One way to add H2(aq) to your input deck is to swap it in for O2(aq). I hope that helps, Tom Meuzelaar RockWare, Inc.

This problem was resolved via personal correspondence. Tom Meuzelaar RockWare, Inc.

Hi Kelvin: Have a look at the extrapolate command on page 32 of the GWB v8 reference manual. The extrapolate option makes a polynomial fit of log K data for a database species across the database temperature range (0-300C). Whether or not it is a good choice to turn this feature on is at the modeler's discretion, but use it with caution. I do not understand your second question.... You can look at the equations for the water stability limits, as well as the equations used to set up the main diagram by looking at the Act2 output file, which you can access via the Run - View - .\Act2_output.txt menu option. I hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Kelvin: We have not optimized GWB to run on non-English language operating systems, so I'm afraid this is not a trivial fix. However, once you have finished modeling, you can easily export your image as a vector file to a program such as Adobe Illustrator or Photoshop and fix the details (via the File - Save image menu). Hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Lou: Here is the correct portion of the manual: The reference is as follows: Phillips, S.L.H, H. Ozbek, A. Igbene and G. Litton, 1980, Viscosity of NaCl and other solutions up to 350C and 50 MPa pressures. Lawrence Berkely Laboratory Report LBL-11586, 71 p. Let me know if that resolves it for you. Regards, Tom

Hi Denis: It looks like the trouble begins as soon as Analcime starts precipitating- I believe the problem is the Analcime is saturated- Q/K = 1, or log Q/K = 0. Given that you are using the built in rate law, which has a (1-Q/K) term, you essentially have no thermodynamic drive for your Analcime precipitation. I hope that moves you along. Regards, Tom

Oops- sloppy. I posted the wrong part of the manual. Viscosity in Basin2 is calculated via either a lookup table or equation- as soon as I figure which one GWB uses, I'll post the correct info here. Regards, Tom

Lou: Density calculations are given as follows (the equations are taken out of UIUC's Basin modeling program guide): I hope that helps. Regards, Tom

Hi Stefan: Can you email me the pertinent scripts (not all 100 are necessary...) to see if I can reproduce this? Regards, Tom Meuzelaar RockWare, Inc.