Jia Wang

Hello, I don't have access to the paper linked, but if you have other information such as the standard change in enthalpy for the reaction, you can calculate the equilibrium constant at another temperature using the Van't Hoff equation. The GWB apps also is able to extrapolate using an internal polynomial expansion. For more information on the extrapolate feature, see the GWB Command Reference. The option to enable is located in the Stepping dialog in React and X1t. For more information on extrapolate, see the GWB Reference Manual. In general, I would advise caution when extrapolating log K's for temperature beyond the range of validity prescribed for the reaction of interest. The further you extrapolate outside the range prescribed, the less accurate the values may become. Hope this helps, Jia Wang

Hello Vincent, The hypothetical water composition is just an example to demonstrate the mass transfer concept . The Geochemical and Biogeochemical Reaction Modeling textbook states that the hydrolysis of potassium feldspar is the first reaction path traced using a computer in Helgeson et al., 1969. Perhaps that paper will have more information regarding how the starting composition was chosen. Helgeson, H. C. (1969) Thermodynamics of hydrothermal systems at elevated temperatures and pressures. American Journal of Science, 267, 729-804. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Nourah, With React, you are able to set up and run multicomponent reaction modeling. Since I am not sure the exact type of problem you are looking to solve, I would give a few simple suggestions on where to start with React. In React, you would need to constrain the initial composition of your system in the Basis pane. Here you would set the concentration of components based on any lab analysis, swap in any minerals that may be in equilibrium with the fluid, or setting a gas buffer. Then you would need to decide which type of reaction path is appropriate for your specific problem. The sliding fugacity model you described in the original post is one type of many reaction paths possible. Other reaction paths include: titration paths, in which reactants are added or removed gradually; polythermal paths, in which temperature varies; kinetic paths, in which rates of reactions are controlled by a kinetic rate law. Additionally, React also have special configuration paths that are useful for specific scenarios, such as the flow-through model that prevents precipitated minerals from redissolving, and the flush model that is allows users to displace the existing fluid from the initial system with the reactant fluid. For detailed examples on using React, please refer to chapter 3 of the GWB Reaction Modeling Guide. There are also a variety of fully worked examples available on the GWB Academy. If you have a specific problem that you would like to troubleshoot, please post a description of what you're aiming to do along with the relevant input files and thermodynamic datasets. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, I want to let you know about an additional method to overlay Quartz and Am. silica solubility to your diagram. You can create a solubility diagram for Quartz and Am. silica in addition to your main stability diagram, then copy each to PowerPoint as an enhanced metafiles, ungroup, and assemble a composite diagram. You can create a simple Quartz diagram like in Act2 like by using this set of commands: diagram vs SiO2(aq) diagram SiO2(aq) diagram on Na+ swap "Na+/H+" for Na+ To create a diagram for Am. silica solubility, you can suppress the most stable forms using the suppress command (suppress Chalcedony Cristobalite Quartz Tridymite). Hope this helps, Jia

Hello Vincent, Just a couple more thoughts to add to my previous response. The vol % is the volume of minerals relative to the volume of your bulk system (fluid volume + mineral volume + inert volume). So for example, if your bulk system has a total volume of 1000 cm3, then 10 volume % of a albite would occupy 10% of the total volume (100 cm3). For equilibrium calculation, the mass or volume of mineral does not matter, so you should focus on getting the initial assemblage right. Once you have the mineral assemblage correct, you can then worry about adding back in the exact values. Additionally, you might also want to consider the redox conditions in your system. Is N2(g) in equilibrium with NH3(aq)? If they are not, then they should be decoupled and each redox state constrained separately in your model. Best regards, Jia

Hello Erik, The installer from the updates page is a patch and not the full installer. I have sent a new installer download link to the email address you provided at the time of your Forum registration. Please check your spam folder if you do not find it in your inbox. Please let us know if reinstalling with the full installer resolved the issue with RXN. Best, Jia

Hello, The grey lines for Quartz and Amorphous silica looks to be super imposed on top of the stability diagram in the original publication. If you would like to add these lines to your Act2 diagram, the easiest way to do so would be to export the plot and add the lines in a graphics editor, like Powerpoint or Adobe Illustrator. On a slightly different note, Act2 allows user to overlay data points on top of the diagram, provided that the axis variables exist in your GSS dataset. If you like, you can create a dataset to scatter data points for where you will like to draw the lines, they can serve as guides for you in your graphics program. For more information, please refer to section 5.7 Scatter data in the GWB Essentials User Guide. Best regards, Jia

Hello Vincent, In the software, you can specify components as free or bulk quantity for most entries. For example, you can constrain the sodium component in your basis pane by setting a bulk quantity, which would include the total amount of sodium present in all sodium bearing species. Alternatively, you can also set a quantity for the free sodium ion, which does not include the mass of sodium in Na-complexes, and have the software calculate bulk composition. For more details and examples, please refer to section 7.2 Equilibrium models in the GWB Essentials User Guide. A mineral volume will always be treated as a free quantity, meaning that the value you set in the basis will only reflect the volume of the mineral and should typically be the case for minerals. I think it's unlikely that all the minerals observed in the composition are in equilibrium with respect to a fluid at the same time. You said that you were able to set up the problem to converge with just the fluid phase previously, so I would suggest you use that as a starting point. If you think a mineral is in equilibrium with the fluid, you can try swapping in the mineral and then run the calculation. You can try doing that for multiple minerals until you have something that seems reasonable. You can also double check that other values such as gas partial pressures and the eh are reasonable. It seems like the mole fraction of CO2 is about 0.96 with a total pressure of 96.1 atm but 40 bars was entered. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Erik, This seems to be a very strange issue and I am not sure what might be causing. I have spoken to our technical team and they recommend that you try closing all GWB apps and then running the installer again. Could you please try that to see if it resolves the issue? If you need a link to download the installer again, please let me know and I will be happy to provide one. Best regards, Jia

Hello Erik, I am not sure what the issue may be, but I can try to help. When trying to launch RXN, does the software give any warning or error message? Does launching RXN from the GWB dashboard make any difference? Does this occur with any other GWB application? Please try the solutions in the General tips of unresolved section to see if they help. If not, please provide a screenshot of any error messages encountered. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, I’m sorry to hear you are having issues with the GWB font. Please download and then install “GWB Symbol Ext” Font directly from the GWB website. For step-by-step resolution, visiting the GWB installation troubleshooting page: https://www.gwb.com/installation_troubleshoot.php#RESOLUTIONS Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, Thanks for posting your input file. After taking a look, I noted that you are plotting the Eh-pH diagram for manganese as the main species. Act2 calculates equilibrium equations, which is then assembled in a 2-D grid to show the stability of minerals and predominance of aqueous species (based on the highest activity). Based on what you described in your previous post and here, regarding coexisting minerals, I think you require the calculation of speciation at various pH and Eh. This is not something Act2 is intended for. Phase2 on the other hand solves a complete multicomponent system (accounting for speciation) at each node in the grid and reports the most abundant species or mineral in its predominance diagram. You can also create mineral assemblage maps, which will show you which mineral or group of minerals is present in the node. You can see an example of this in section 8.1.2 Assemblage Maps of the GWB Reaction Modeling User Guide. If you would like to tryout Phase2 (or other more advanced GWB applications), please fill out our request form and we will be happy to send you a demo license. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, The calculation for the pore volume change assumes a constant bulk volume for the initial and final state of the system. For the NaOH flood example, the initial bulk volume is the sum of the fluid volume (1064.535) and the mineral volume (6050) at 7114.53 cm^3. Calculate the initial porosity by dividing the initial mineral volume (1064.535 cm^3) by the bulk volume to get 0.149628. After 20 days of flushing the system, calculate the final porosity by taking the initial bulk volume (7114.53 cm^3) and subtract the initial mineral volume (6050) and the additional mineral volume precipitated during the simulation (98.74367 cm^3) and then divide by the initial bulk volume. This will get you a final porosity of 0.135748. Calculate the change in porosity by taking the difference and dividing by the initial porosity: (0.135748-0.149628)/0.149628 = -0.092763 To calculate the fraction of alkali consumed, you can look at the increase in moles of Na+ in the rock (under the Variable type Components in rock) and divide it according to the moles of Na+ in the reactant fluid. In the NaOH flood simulation, the Na+ in the rock component increased by 3.926 moles. We know that 5 moles of Na+ were added to the system (recall that the reactant times factor was set to 10). The fraction of alkali consumed is 3.926/5 = 0.7852. With regards to your follow up question, I think you missed accounting for dawsonite in your carbonate totaling. Since the kinetic rate law was only set for Quartz, all other minerals in this system are precipitating and dissolving according to simple thermodynamics. Hope this helps, Jia Wang Aqueous Solutions LLC

To follow up with my previous post, the nature of these types of activity diagrams do not account for complexation of the ions with each in the "in presence of" section. If you are interested in more complex phase diagrams, you can try the Phase2 application. Phase2 solves a set of equations to describe the distribution of mass, just like SpecE8 and React, at each node in a 2D grid. You can constrain the composition of a fluid in terms of concentration, rather than activities and set up reaction pathways, along the x and y axis. You can visit the Phase2 web page for information or see examples in the GWB Reaction Modeling User Guide. Best regards, Jia

Hello, I am not sure I understand the goal of your activity diagram. Are you trying to see which sulfur species/mineral (pyrite vs. alabanite) is predominant under varying Eh and Ph conditions? In that case, I would suggest that you use SO4-- as the species you diagram. Set the x and y axes as you have done before. Then in the "in presence of" section, add in the log activity for your Mn++ and Fe++ and select speciate over x-y for both components to allow speciation according to Eh and pH. I think this will be a good starting point for you. If you still have issues with your diagram, please post a complete clear description of the issue along with any input file so we can take a closer look more easily. Just a general tip for creating activity diagrams. Note that all minerals, aqueous and gas species in the thermodynamic dataset loaded are considered in all calculations. If some of these species in your diagram are not expected in your field site or experiment, you can use the suppress feature to exclude them from the program's calculation. For more information and example on suppress, refer section 4 in the GWB Essentials User Guide and the Command Reference. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, A good place to start is to calculate the free energy change for the reaction of interest using the delta H and S provided in the supplementary document for your reaction. This value will depend on the species in the reaction. Once you have the change in free energy, you can solve for the equilibrium constant at standard temperature (25C) using the equation delta0G = -RT*ln(K_eq). I believe a similar thread discussing this and can be helpful for you: https://forum.gwb.com/topic/2106-glass-chemistry/ I would discourage copying and pasting data entries across datasets unless you are sure that the entry is consistent with the activity model intended for destination dataset. For example, thermo_freezechem.tdat and thermo_coldchem.tdat uses the Harvie-Moller-Weare formalism of the Pitzer equations to calculate activity coefficients. thermo.tdat and thermo.comV8.R6+.tdat are datasets that use the Bdot activity model. Therefore, copying and pasting entries across the datasets may result in very erroneous results. You can find the activity model for each dataset at the top of the file (if you open it in a text editor) or on the Header pane (if you view the dataset using TEdit). Another thing to note is that the log K format for each dataset may be different. For some datasets published, a six term polynomial is used to express the log equilibrium constants within a temperature range. For example, thermo_freezechem and thermo_coldchem both give their log k values as polynomial expansions. The coefficient to fit the polynomial is given for the entry. You should note that these coefficients are not the direct log K (e.g. Natron Na2CO3•10H2O from freezechem in your excel spreadsheet). If you would like to see the log Ks at the principal temperature specified in the Tables tab, you can go to the Header pane and switch the log K format from polynomial to table. TEdit will calculate the log K at those temperatures for you. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello again, If you are interested in ideal site mixing, you can edit the thermo dataset to include factored versions of the end members, scaling the stoichiometry such that the site mixing parameter for your binary solid solution is equal to one. By doing so, ideal molecular mixing and site mixing becomes equivalent. Hope this helps, Jia

Hello, The ideal solid solution model currently does not accommodate site mixing. Please refer to section 2.5 in the GWB Essentials User Guide for more information on solid solution models supported in the GWB. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, There are a couple of options for this. In some dilute fluids, you may assume that the activity coefficient is close to 1 and the molal concentration roughly the same as the activity. If you have a fluid analysis, you can also use SpecE8 to calculate the distribution of mass amongst species. SpecE8 will also report the activity for each species which can be used to set up your Activity diagram. For more information on using SpecE8, refer to section 7 in the GWB Essentials User Guide. Hope this helps, Jia Wang Aqueous Solutions LLC

You're welcome. I am glad to hear that you are able to find a workaround solution for now. This issue is very strange and we have not had any other users report it. After speaking with our support team ,they had a few suggestion as to the cause and next steps in troubleshooting. The description of the taskbar icon sounds like another application (some kind of screenshot application?) is interfering with Gplot. If so, you may need to find the application and close it. Another possible issue is a hardware malfunction with your mouse. If the mouse is double-clicking when you are launching the plot, that may result in some weird behavior. If you have another mouse available, it wouldn't hurt to give that a try. Lastly, you might also want to consider adding the GWB program as an exception to your antivirus software. While most antivirus software allow users to deactivate temporarily, it not completely turn off in the background. To ensure that is not the case here, you can just add the GWB as an exception. Hope this helps, Jia

Hello, Thank you for providing more information and trying my suggestions above. I have a couple other suggestions for you to try troubleshooting with. Please close all GWB applications and right-click on the installer and run it as Administrator. Once installation is complete, please try opening existing Gtplot files (ending in .gtp extensions) and new React/SpecE8 output files from runs. You can also try disabling your anti-virus software and/or firewall temporarily to see if either is blocking normal access to your Gtplot. Lastly, we could check your input file set up for anything that may be lead to this issue. Could you please attach an input file that's giving you issue so we can take a closer look? Best regards, Jia

Hello, After taking a quick look at your input file, I have a couple of suggestions to help you get started. Activity is not the same as concentration. If you enter a bulk concentration for Fe++, the program will calculate the distribution of mass amongst dissolved species and precipitated minerals. Do you have a measured value? If you are simply titrating an amount of iron into the system, you can set the initial amount to be very low and then add in a Simple Aqueous reactant for Fe++ in the Reactants pane. Since you're adding a Fe++, you would also want to add an equivalent of anion that balances out the charge (e.g. Cl-). I would not suggest setting a sliding activity activity path. I noticed that you are using Cl- as your charge balancing species. In your case, most of your components are anions and therefore, you might consider using a cation as your balancing ion. I also noticed that you swapped out O2(aq) for NH3 and swapped in NO2- for NO3-. When this is done, the concentration for the nitrogen redox species is used to set the oxidation state of your system. If you wish to constrain the concentration for NO2- and NH3 separately, you can decouple the redox species (NO2- and NH4+) from its basis species (NO3-). After decoupling, you would be able to add NO2- and NH4+ directly. You can then swap in NH3 for NH4+ if you wish. For fore information redox disequilibrium, please see section 7.3 in the GWB Essentials User Guide. Note that the time variable on the Basis pane is used for reactions involving kinetic rates. The program only considers equilibrium reactions unless a kinetic reaction (mineral, aqueous complexation, etc) is specified in the Reactants pane. You can uncheck the time parameter and your model will output the same results. For more information on kinetic reactions, see chapter 4 in the GWB Reaction Model User Guide. A tip for general troubleshooting is to always start simple and then add complexities. The first step is to check whether the initial chemical constraints for your system are allowing the software to solve the equilibrium state of your system before any reaction takes place. You can do this by selecting the Go initial option under the Run menu. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, GSS can use SpecE8 to calculate various secondary values based on the data provided in the spreadsheet. The program solves the problem with a numerical scheme that does not tolerate zero masses well. This is probably the issue with the two samples that failed. You can set the program to treat 0 value entries as no data. To enable this got to Analysis -> Options. You can also just remove the 0 value from the datasheet. For more information on calculation with SpecE8, you can refer to section 3.3 in the GWB Essentials User Guide. You can also investigate issues with a specific sample by launching a SpecE8 instant from GSS. Please see section 3.5 Launching SpecE8 and React in the GWB Essentials User Guide. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, You can reset to the default configuration setting in GWB plotting apps by going to the "File" menu and then selecting the option "Reset Configuration". Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, Thank you for pointing out the confusion with the wording here. In this case, the first fluid is referring to the seawater composition in the Basis pane, which contains a high amount of sulfate in solution . The second fluid is referring to the barium rich solution in the Reactants pane. It is clearer if we examine the concentration vs mixing fraction plot, which shows that high sulfate concentration is present at a mixing fraction of zero. At a mixing fraction of 1, we see a high concentration of barium and practically no sulfate. We will update the Academy in the near future to clarify the explanation. Just an additional note, it is not typical for users to set a reactant times factor when creating a flash diagram. In this case, your injectate is scaled by a factor of 100 whereas your groundwater fluid is not. Perhaps this is causing some unexpected behavior in your model? Best regards, Jia