Tom Meuzelaar

Hi: Currently there is no provision for sorption kinetics in GWB. However, this functionality is planned for an upcoming release. Regards, Tom Meuzelaar RockWare, Inc.

Hello: The thermo.dat database is configured for work at 1 atm system confining pressure. GWB is able to calculate fugacity values for individual gases in equilibrium with the fluid. In most cases, increasing the confining pressure of your system will have little effect on the equilibrium constants in the database. However, for CO2 this is not the case. To calculate accurate CO2 solubility at higher pressures, I recommend you look at the work of Duan et al., specifically: Duan, Z., and Sun, R. (2003) An improved model calculating CO2 solubility in pure water and aqueous NaCl solutions from 273 to 533 K and from 0 to 2000 bar, Chemical Geology, v193, p. 257-271. Duan, Z., Sun, R., Zhu, C. and Chou, I. (2006) An improved model for the calculation of CO2 solubility in aqueous solutions containing Na+, K+, Ca2+, Mg2+, Cl-, and SO42-, Marine Chemistry, v98, p. 131-139 I also recommend the tools available online at: http://www.geochem-model.org/models.htm I hope that helps, Tom Meuzelaar RockWare, Inc.

Wish I could help more, but this is the forum for Geochemist's Workbench users. We have a different program, Act2, for creating Eh/pH diagrams. Regards, Tom

Hi Monica: This link might help: http://www.phreeplot.org/PhreePlot.pdf Regards, Tom Meuzelaar RockWare, Inc.

Hi Nancy: Welcome to the forum. I don't have much knowledge about the thermo data at that pH range. Hopefully, someone with a better background can address this. I can, however, point out two references to get you started: The reference for the LLNL database: "Delany, J.M. and Lundeen, S.R. (1990) The LLNL thermochemical database, Lawrence Livermore National Laboratory Report URCL-21658, 150 p" In the extended LLNL database (thermo.com.v8.r6+.dat), a reference to the data source is given on a species by species basis. Hope that helps, Tom Meuzelaar RockWare, Inc.

**The August 12-13 course is now sold out. We have added a second workshop on Aug 19-20. If you are interested in attending, email RockWare** Dear GWB users: We are pleased to announce a summer workshop in Prague, Czech Republic (coincident with the Goldschmidt 2011 Conference) for GWB Essentials, Standard and Professional. The August 19-20 (Friday-Saturday), 2011 workshop is designed for: Current users of GWB Essentials, GWB Standard and GWB Professional who wish to become more familiar with the software's interface and features. Those interested in reviewing the basics of geochemical modeling (speciation models, activity models and activity diagrams) Those interested in learning detailed reaction path modeling (using redox disequilibrium, kinetics, and surface complexation) Those interested in learning the basics of 1D/2D reactive transport modeling Registration fees are $899 (commercial) / $799 (academic). Students can register on stand-by for $299. The course does not include access to a computer, you will need to provide your own laptop. However, you do not need to have purchased or installed GWB - we will install the latest version on your machine for the duration of the course. Participants who do not own or wish to travel with a laptop may rent one for the duration of the course at additional cost of $175 (choose registration option with computer). Computer will be setup with software installed upon arrival. The workshop room (in the Prague Congress Centre) seats up to 15 participants. If the course is sold out, and significant interest remains, we will consider holding a second workshop during the conference. For all the details, visit the Prague workshop page on the RockWare website. Please don't hesitate to contact me with any questions. Regards, Tom Meuzelaar RockWare, Inc. 2221 East Street Golden, CO 80401 ph. 303 640 5526

Hi Rosario: That depends on your model objectives. However, when you choose Run-Pickup-Reactants-Entire, any minerals remaining in your system at the end of your titration will be represented as mass of component. In other words, they won't show up as swapped in for a component as they would in the Basis. Hope that helps, Tom

Hi Rosario: Titrate aragonite and calcite (Reactants) into seawater (Basis) Use the Run- Pickup- Reactants command to add this mixture to your Reactants tab Load your new fluid into the Basis using the File- Open command Hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Diana: No current plans. Many years ago, we offered a network license. However, it was requested so little that the overhead costs of network license maintenance outweighed the benefits of offering it. If this changes, we will consider offering this as an option again. Regards, Tom

Hi Elisabeth: Your temperature settings are correct, but the 'flash' option is preventing proper polythermal mixing from occurring. Can you explain a little more about what the purpose of this model is? Regards, Tom Meuzelaar RockWare, Inc.

Hi Diana: Remote desktop will not work with your hardware lock. If you switched to a flexLM license file, you'd run into similar limitations- FlexLM licenses can support terminal services (remote desktop), but this option is left turned off. The main reason for this is that it would allow multiple users logged in at once to use the software, which is a violation of the end user license agreement. Hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Joel: I have seen this message before, but it's not always diagnostic. I'd be happy to look at your X1t script if you want to attach it or email it to me. Regards, Tom Meuzelaar RockWare, Inc.

Hi Mooketsi: To build this model- Use the React model Load your water into the Basis pane Titrate your gas in via the Reactants pane For now I would ignore the organic phases, as they will introduce additional complexity that is probably unwarranted at this point. Note that you will need the right basis species representatives for each gas you titrate in. For instance, if you titrate Methane into the model, you'll need to constrain the oxygen component (either dissolved oxygen or Eh) in the Basis. Also, to model gases such as Argon, Carbon Monoxide and some of the organics, you'll want to use the extended Lawrence Livermore thermodynamic database (thermo.com.v8.r6+.dat). Hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Joel: This happens to all of us. I actually appreciate you posting this. There are no mundane questions, and the greater user community benefits from seeing these problems worked out online. Regards, Tom

Hi Joel: 'Reaction mass imbalance' errors usually refer to a problem with the molecular weight. I notice that your two problem entries have only have 3 digits after the decimal on the molecular weight - the GWB thermo databases require 4. Second, and more importantly, be sure that your molecular weight reflects the summation of the basis species in your reaction (multiplied by the stoichiometric coefficients), using the individual mole weights given in the Basis species section near the top of the database. Let me know if that gets you there.... Regards, Tom

Hi Ruth: Not that I'm aware of. You can always go back and look at the source of the data, and look at the literature related to the experiments. You can also bracket your results to show the range of model sensitivity due to differences in the solubility data. Hope that helps, Tom

Hi Ruth: The polynomial fit equation for gypsum solubility is given by Rxn as follows: Calculated saturation indices are dependent on more than the equilibrium constants given PHREEQC or Lawrence Livermore database (the 'K' in the saturation index); the 'Q' component depends on calculated speciation activities for Ca++ and SO4--, which are dependent on the thermodynamic data for all of the other dissolved species in the solution matrix. The PHREEQC and LLNL database have different dissolved species entries and equilibrium constant values, so the speciation output probably varies somewhat. These are great questions to ask of your model, by the way. Many modelers ignore looking at these details, and sometimes you will get significantly different results simply by using a different database. Regards, Tom

Hi Ruth: I am able to reproduce the log K for Gypsum that SpecE8 calculates (-.1443). A couple of key points in making your calculation: Be sure to use activities, not molalities in your calculation (the log activities for Ca and SO4 are reported in the speciation output, so just take the inverse log) Be sure to adjust the equilibrium constant to reflect the temperature you are working at (46.9C). The Rxn module is a handy tool for doing this- put in the reaction for gypsum, and look at the polynomial fit in the output pane (I calculate a temperature adjusted log K of -4.503723) Let me know if that gets you there. Regards, Tom Meuzelaar RockWare, Inc.

Hi Laura: Ok- I understand now. No, you cannot do this in Gtplot. However, if you export the image as a vector file (File - Save Image As...) then you can create your final image in a third party image modification application (such as Adobe Illustrator or Photoshop) that is better suited for such tasks. Hope that helps, Tom

Hi Laura: When it comes to plotting GSS data in Gtplot, you can group symbols by sample or analyte: Be sure to set the appropriate symbol, color and size in the GSS spreadsheet. If you want to plot groups of samples or analytes, give them the same symbol In the Gtplot module, choose Edit - GSS data... and then choose to plot your symbol type, symbol color and symbol size by either sample or analyte Let me know if that answers your question. Regards, Tom Meuzelaar RockWare, Inc.

Hi Rosario: Start by correcting the kinetic rates. At that point, you made need to fix pH or make other adjustments. I'm happy to take a further look.... Regards, Tom

Hi Rosario: I don't think the rate parameters are entirely behind the issue- kinetics is still driven by equilibrium. In your model, initial equilibration of seawater with calcite and aragagonite drives both minerals from undersaturation (dissolution) to supersaturation (precipitation). Given that the kinetic rates for both are identical, the mineral with higher thermodynamic stability (calcite) precipitates. Additionally, the rates you've set are so high that the model proceeds according to equilibrium and you have simple conversion of aragonite to calcite. I would fix this model by looking at two issues: 1. set realistic kinetic rates for calcite and aragonite for the timeframe you've specified. 2. try to set up initial equilibrium between seawater and aragonite/calcite in such a way that they are not initially supersaturated. I hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Rosario: If you can attach a script, I'd be happy to take a look. Regards, Tom Meuzelaar RockWare, Inc.

Hi Thomas: The problem is exactly as the error message states- in your custom database, you have H2S as a basis species, and SO4-- as a secondary species. So swapping H2S in for SO4 is no longer appropriate. You should be able to add H2S in directly as a basis species, assuming the database is formatted correctly. Hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Marty: There's a couple places you can go. First, in the GWB Reactive Transport Modeling Guide: Page 17 tells you how to configure unsaturated media Page 40 gives you a simple model of weathering within a soil profile in the presence of a CO2 gas buffer Second, you can get more detailed information by reading section 27.2 in Craig's Geochemical and Biogeochemical Reaction Modeling textbook. I hope that helps, Tom