Jia Wang

Hello, I am not sure what your diagram would show if you were not able to complete your simulation due to the ionic strength error. Were you able to launch P2plot after running the attached input file? Your file attached has the sliding path set to 10 Volts, not 10 millivolts as you stated above. When I changed the unit in the Y Axis pane from V to mV (by clicking on the unit "V" and selecting "mV"), and ran the simulation, it went to completion and I was able to plot various Predominance diagrams. In this new file, I noticed that you swapped in Ni(OH)2(s) for your Ni component. Was this intentional? Doing so would set the initial concentration of Ni in the fluid in equilibrium with Ni(OH)2(s). I am not really sure what you mean by not much of a difference. If the reactions and species that you expect are not present in your simulation, you would need to check if they are present in your thermo database. Also, remember that the predominance diagrams only show the highest abundance species or mineral at each node. You can investigate further the concentrations and minerals present if you plot a slice of the grid, across or along scanning paths. You also have the option to plot a Mineral Assemblage diagram under the option Format menu. For more information on Phase2 plot configurations, please see section 8 in the GWB Reaction Model User Guide. Hope this helps, Jia

Hello, I apologize for the delayed response. We don't get alerts for new posts in the archive pages. I have moved this thread to the front page. Here are a few quick suggestions to help you get started: With the "diagram species" selection, you choose the main species for which you want information. In this field, you can choose to select an aqueous species, mineral, or gas to diagram. The "in the presence of" field is used to modify the form of the main species by adding species and minerals that the main species can react with. It seems like this diagram is similar to one of the examples, Aluminosilicates.ac2, in section 5.1 Diagram calculation of the GWB Essentials user guide. I would suggest that you start there if you do not have any additional information. All the minerals in the diagram are Al-bearing minerals, so I would keep Al+++ as the diagram species and swap it in for Kaolinite. The input file assumes the fluid is in the presence of Quartz. Adjust the temperature to 260 Celsius and then examine the diagram. Note that Act2 includes all minerals in the thermo dataset loaded by default. I suppressed some of the clay minerals (Beidellit-H, Beidellit-Ca, Heulandite, etc) until I manage to get most of the fields in your plot. Does the literature that this figure come from have any additional information regarding what was used in calculating this diagram? Without additional information, it would be difficult to proceed. Also, I believe the dashed lines for the carbonate system is calculated separately and layered onto the same plot. You can create a separate diagram and overlay the two diagram for the composite in a graphical editing program like PowerPoint or Adobe Illustrator. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Scott, You're welcome. Portlandite is swapped into the system because the mineral is in equilibrium with the fluid at the end of the simulation. If you look at the reaction for portlandite in the thermodynamic dataset, you can see H+ in its reaction. In any of the reaction modeling applications, you can swap in a mineral for a component that it's composed of to constrain the concentration by being in equilibrium with that mineral. Best, Jia

Hello, I am not sure if I understand some of the commands in your script. I am not sure why Quartz is swapped in for SiO2(aq) at the top of your input file. Was this intentional? When you later set SiO2(aq) = 9e-7 molal, you effectively unswapped your mineral. Again, you titrate in some mass of quartz but your description of the problem and the caption of the figure does not mention quartz being titrated. Could you double check the conditions for your initial system? A general tip when recreating these types of results is to try to use as much of the same conditions as possible. In general, you should check the equilibrium constants for the reactions in your dataset against what they use. You would do best if you are able to use their exact mineral reaction instead of approximating with an alternative dataset. Perhaps the authors provided additional information regarding how they performed the calculation in supplementary materials or appendices. If you believe that your set up is correct, you might inquire one of the paper's original authors for the input file to compare. Best regards, Jia Wang Aqueous Solutions LLC

Hello Sofia, I am sorry to hear about this. I am not sure why the font installation didn't resolve this issue. Could you please check that the font file installed successfully after you downloaded it from the website? Double-clicking on the font file should open a window that has the option to "Print" or "Install" on the upper left hand corner and you should've clicked "Install". If you had successfully installed it, could you please check that it is in your font folder on your system? You can check by going to the Control Panel on your machine, select Appearance and Personalization, and open the folder "Fonts". Check if the font "GWBSymbolExt" is there. Best regards, Jia Wang Aqueous Solutions LLC

Hello Jueun, Thank you for attaching your scripts. Here are a few suggestions to help you get started with troubleshooting, I first ran a "go initial" run with your Phase2 input file. Doing so shows the error you mentioned above, so right away, this tells you there's something not quite right with the way your basis is set up. So before adding any reaction paths, I suggest taking the composition in your basis pane to React and start troubleshooting there. Based on the concentrations of your components, I don't think the fluid is really out of ionic strength range. If your starting pH is very low, then swapping in a more abundant species for the corresponding component is going to help the program solve the equilibrium state. In particular, SO4-- is not going to be the most dominant form at pH of 1, swapping in HS- helped with the initial calculation. Similarly with the carbonates, CO3-- is presently at very small quantity at low pH and swapping in CH4 seems to help. I initially tried CO2(aq), but given the low Eh, CH4 is likely to be abundant. Charge balancing ion is typically defaulted to chloride because of its high abundance in many natural waters. In this case, your most abundant anion is Fluorite, so I would use that as the charge balancing ion. Once you have gotten React to solve the speciation of initial composition successfully, you can return to Phase2 and adjust your X and Y axis. I noticed that you have set the Eh path to slide to 50 volts, which seems really high. To get an idea of the range for pH and Eh, I built a simple Act2 diagram for Ni++ (diagram Ni++ as the main species and assign pH and Eh as axes) and see that the water stability limits range between -.5 and 1.25 Volts across the range of pH. If you are going too far outside of this range in Phase2 or React, the program will fail because it can't calculate equilibrium when water is not stable. Unlike Act2, Phase2 and React solves a full solution to a multi-component chemical system. On the other hand Act2, simply solves the equilibrium equations used in assembling an activity diagram. These equilibrium equations can be solved for at any range of pH and Eh. Because Phase2 is essential solving a series of reaction models that include mass balance and activity calculations, it is oftentimes necessary to choose a narrower range for the variable changing in the x and y axis. For more information on Act2, please refer to chapter 5 of the GWB Essentials User Guide. One tip for using Phase2 is to always start with a relatively coarse grid. By default, the grid is set to 301 on the X and Y axes but you can adjust this by going to Config -> Output... I suggest starting with a smaller grid (e.g. 20 by 20) so that you can save time until you are ready to make a more detailed diagram. For more information regarding Phase2 configurations and examples, please refer to Chapter 7 in the GWB Reaction Modeling User Guide. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Scott, The values reported in the Original Basis reflect the bulk concentration of each component in the system, which can consist of negative masses. The concentration of any species themselves may be very small but not negative. As an example, imagine a system consisting of only the components of H2O and H+. With this system you can form species H2O, H+, and OH-, where OH- = H2O - H+. In a highly alkaline system, which your attached script is, the amount of OH- is going to be greater than H+, and the overall solution is described by a positive amount of water component and negative amount of H+ component. For more discussion on this, please refer to Chapter 3 of the Geochemical and Biogeochemical Reaction Modeling text. When you use a pickup command for the entire system, this will set the fluid composition and any minerals in equilibrium with the fluid as the new Basis. In this case, Portlandite and Magnetite are swapped into the basis for H+ and O2(aq) components respectively. React performs the swapping automatically at each time step to find the equilibrium state, where no minerals are supersaturated. As a simple example, you can run the following script in a new React: SiO2(aq) = 10 mg/kg go In the Results pane, you will see that React had swapped in Quartz for SiO2(aq) since the fluid was supersaturated with respect to Quartz and a small amount of mineral is precipitated. If you now pickup the results as your basis, you will get Quartz swapped into the system for SiO2(aq) and the amount of mineral precipitated. If you would like a more detailed example of this, please refer to Chapter 6 of the Geochemical and Biogeochemical Reaction Modeling text. Btw, I have moved your post to the front page, where we get alerts when a new post is added. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, The software is capable of modeling both two-layer and triple-layer surface complexation reactions in addition to a wide range of more simple sorption processes (e.g. distribution coefficient approach, freundlich isotherm, langmuir isotherm). You can chose the surface model that's best suited for your problem based on the details provided for each type in section 7.7 Sorption onto mineral surfaces in the GWB Essentials User Guide. Once you determine the type that is most suitable for your work, you can use the surface reaction datasets provided (Gtdata folder where GWB is installed) as templates for customizing a reaction datasets you can use for your calculations. Only one water sample can be loaded in a SpecE8 instance at a time. You can, however, launch multiple SpecE8 samples at the same time in GSS. Please refer to section 3.5 Launching SpecE8 and React. Hope this helps, Jia

Hello, If you are encountering this error message when you open an existing GSS file, then the software is not able to find the file "thermo.tdat" in C:\users\GJones\OneDrive - Brown and Caldwell/Documents\Hydrogeo Essentials\Geochem Modeling\Gtdata\. Perhaps your thermo dataset or Gtdata folder was moved? Could you check if that's the case? Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, In Gtplot configuration, you would select the Variable type "Surface parmeters" and see the option for "HFO surface charge). You can select this for one of the axes and pH value (under Variable type "Chemical parameters) on the other axis. Please note that this variable type would only appear if you have loaded a surface complexation reaction dataset for your run. For more information on configuring XY plots in Gtplot, please see sections 6.2 in the GWB Reaction Modeling User Guide. Hope this helps, Jia

Hello Kovalenko, SpecE8 solves the chemical mass distribution of species at equilibrium given a complete chemical analysis of a fluid. If you are using a two-layer surface complexation model, you can plot the pH vs the surface charge after the calculation is finished. To find the point of zero charge, you can recalculate at different pH values until you get to a surface charge of 0 in SpecE8. If you have access to the Standard and Professional Edition, you can use React to set a sliding pH path to scan across a range of pH values. This way, you can view a range of surface charge values corresponding to the pH values. Best regards, Jia Wang Aqueous Solutions LLC

Hello, Here are a few suggestions to help you get started. Since you already added your chemical analyses to GSS, you can prepare a calculation by launching one fluid sample at a time in a SpecE8 instance. You can see an example of this in section 3.5 Launching SpecE8 and React in the GWB Essentials User Guide. To model sorption, you will need to load a surface dataset corresponding to the type of surface reaction you are interested in. Depending on the sorption model you choose, your surface data will consist of slightly different parameters. To see all sorption models available in the GWB, please refer to section 2.5 Sorption onto mineral surfaces in the GWB Essentials Guide. A set of surface reaction datasets are distributed with the GWB, you can find all of them in a subfolder named ‘Gtdata’ where the software is installed on your computer. Very likely, you would need to edit the surface datasets distributed with The GWB specifically to your system. I would recommend you create a duplicate of a surface dataset distributed with The GWB and make changes using TEdit. More information on how to use TEdit to edit your datasets can be found in section 9 of the same user guide. With your fluid composition and your surface dataset loaded, you can trigger SpecE8 to calculate speciation. You can look at how sorption changes with pH by going back to the Basis pane and alter the pH before rerunning your calculation. If you would like further help with troubleshooting, please post your SpecE8 input file and the relevant dataset(s) along with a full description of the issue encounter so we can take a closer look. Hope this help, Jia Wang Aqueous Solutions LLC

Hello Jason, Here are a few suggestions to help you get started. You would want to set up the initial system in your Basis pane. Make sure that you input your units for your components concentration correctly. The apps will allow you to enter components in elemental equivalents. You would also need to consider if any redox couples need to be disabled for your simulation. If you are starting in React, you can do a "go initial" run to check that the software is able to solve the equilibrium state of your fluid before setting up any reactions. See section 2 and 7 in the GWB Essentials User Guide for more information on configuring your calculations. You can vary the temperature of your system within the range prescribed by your thermodynamic dataset. The log Ks in each thermodynamic dataset is compiled at a temperature and pressure stated at the top of the thermodynamic file. When you vary the temperature (e.g. via a sliding temperature path) of the system, the pressure corresponds to the temperature set. The confining pressure cannot be set independently, except in Tact and Act2. In Tact and Act2, the pressure set affects the water stability limits and the stability fields for gases, but it does not affect the equilibrium constants of minerals and other aqueous species. If pressure correction is very important, you can compile a thermo dataset at a pressure or temperature of interest. See the K2GWB, DBCreate, PyGCC references on our thermo data page for more info. To set gas pressures, you can instead set gas partial pressure or fugacity. As for varying the pH with concentrated HCl, you would first create a 36% HCl fluid and set that as a reactant. I have described how to create this reactant in a previous post. You can titrate in various amounts until you reach the desired pH levels. You can extract the saturation indices for various minerals by going to the plotting apps for your results. You would plot saturation indices for select minerals vs your variable of interest. Copying from Gtplot and pasting into a spreadsheet would retrieve the numerical values. For more information on this, see 8.5 exporting the plot in the GWB Essentials User Guide. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, The dataset "thermo_minteq.tdat" was converted from Minteq release version 2.4. As the file stated, the H2(g) reaction was not included in the original Visual Minteq data file and therefore it is not available in the converted GWB dataset. You can verify this by reviewing the input data provided at the end of the tdat file (open in a text editor) or in the bibliography section of the Header pane. Note that the GWB does not maintain any datasets, please contact the original author of the dataset with any questions you have with regards to the reactions in the dataset. I am not familiar with the chemistry of hydroquinone, but perhaps another user on the forum who may be more knowledgeable will be willing to reach out. For more information on how to add reactions to GWB datasets in general, please review the TEdit section in the GWB Essentials User Guide. You can also view examples of editing datasets with Tedit here. You can also view the dataset format in the GWB Reference Manual. Best regards, Jia Wang Aqueous Solutions

Hello, The rate law for microbial metabolism isn't quite correct in the way you have entered it. In the user guide, if you are using the dual monod model, you would include both the electron donor and acceptor terms in your equations, however, you wouldn't include the terms for growth yield and decay rate in the same rate equation. To update the biomass in a custom rate law, you would need to call a special function setgwbvar at every time step. If not, the biomass specified will not update from what is entered in the Reactants pane. I believe a custom rate law script or a compiled rate law script will allow you to use setgwbvar to update biomass at the end of every step of the calculation, but not with the equation option. You can see an example of this in section 5.2 of the GWB Reaction Modeling guide. Note that if you use the built in option for your rate law, GWB will automatically update the biomass calculation according to the growth yield and decay rate specified at each step. I think there are a few other small issues in terms of the equation you entered: The equation shown in the user guide also accounts for water mass (n_w), you would also need to do that if you are trying to replicate the default rate law by entering your own custom version. R, is the variable commonly used as the gas constant, but it is not a default value built in. You should enter the actual value of the gas constant. You can find all the parameters accepted in setting up a custom rate law in Tables 5.1. The complete list of helper functions are available in Table 5.2. In the second picture, the rate is figured in terms of molalities of the species "m_Ac" and "m_SO4" but in the equation you entered, the species are accounted for in terms of activity. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, You're welcome. I am glad that was helpful. The GWB applications draw its aqueous species, gas species, and mineral reactions from a thermodynamic database loaded. If the mineral(s) of interest is not in the thermodynamic database, you would need to add it accordingly. For minerals with a fixed composition, you can add in a new entry using the TEdit application. For the new mineral to be considered in the simulation, you must at least designate one log K value for the mineral reaction. You can find more information regarding TEdit, in section 9 of the GWB Essentials Guide. For dataset formats, please see the Thermo datasets chapter of the GWB Reference Manual. Since labradorite and augites are both a part of solid solutions series, you might also consider using one the solid solution models available. Starting in GWB 2022, you can model binary solutions using the ideal molecular mixing or the non-ideal Guggenheim activity model, using either the discrete or continuous implementation. You can add the solid solution to your thermodynamic dataset or configure it within the GWB apps at run time. For more information, please see section 2.5, Solid solutions, in the GWB Essentials Guide. Best regards, Jia Wang Aqueous Solutions LLC

Hello Huan, We are sorry to hear that you're having issue with the old plot files from GWB11. Starting in GWB 12, the output file format transitioned to xml format. Until GWB 2021 (version 15) release, we provided compatibility for legacy files for users to transition to the new format. The current release, and releases going forward, will only support the new format. To get your output files to update, we recommend you to simply rerun your original input scripts. The new output files should have no issues opening in GWB 2022. If you do not want to rerun your original script, please let us know and we can send you a link for the GWB 2021 installer. Best regards, Jia Wang Aqueous Solutions LLC

Hello, It sounds like you have a wealth of information regarding your system. What you described may work, but unless you suppress more stable minerals in from in React, the software will consider all possible minerals given your composition. Minerals that are most stable would be swapped into React in its calculation of the equilibrium state, which won't necessarily be the minerals that you expect according to your mineral assemblage analysis. Please note with React, you should see two Xi = 0 text blocks any time an initial system contains supersaturated minerals and precipitation is not disabled. The first block shows you the metastable equilibrium state of your aqueous speciation after you have initialized your run, where no supersaturated minerals have been precipitated. SpecE8 on the other hand only calculates the metastable equilibrium state of your fluid. More details regarding this can be found in the GWB Essentials Guide and the Reaction Modeling Guide. I would suggest using the mineral assemblage you have taken from your aquifer as a starting point. If you suspect that a mineral is in equilibrium with the composition of your fluid, you can swap in that mineral and then run a speciation calculation to see if the concentration calculated in the fluid matches that component in your chemical analysis. Any other information regarding your system's conditions (e.g. gas buffers) that can help you figure the controls on the fluid composition would be helpful as well. In terms of inputting minerals from the basaltic aquifer, this would depend on the types of reaction. Minerals that react very quickly within your system can be swapped in your Basis pane and treated as equilibrium reactions. Minerals that react slowly but measurable over the course of the time scale of your system can be constrained kinetically. You can add a kinetic mineral reaction (as well as a variety of other types of kinetic reaction) in your Reactants pane. You can also set a mineral that is initially in equilibrium with your system but allowed to react according to kinetics through the simulation. For more information on kinetic reactions, see section 4 in the GWB Reaction Modeling Guide. If certain reactions are relatively slow and does not impact your fluid composition over the time scale of interest, then you might consider excluding them from your model. In a reactive transport model, you would set the composition of the fluid entering the domain in the Fluids pane in X1t and X2t. For more information on boundary fluids, please see section 2.8 of the Reactive Transport Modeling user guide. Hope this helps, Jia

Hello Ali, It sounds like you are on the right track on getting this started. Here are some suggestions that may help. If you aim to build a reactive transport model, then starting in React to build a reaction model, checking if the reactions are behaving in the way you expect before moving to one of the reactive transport modeling apps is a good idea. In React, you would set up the basis pane with the composition of the fluid you wish to perform reactions with. This is also where you would swap in any constraints, such as minerals or gas buffers, that you can assume your fluid is in equilibrium with. You can use the go initial command to check that the program can successfully calculate mass distribution. If successful, you can specify various types of reactions (e.g. kinetic reactions, sliding activity and fugacity paths, etc) in the Reactants pane. If your work requires a reactive transport model, you would need to select whether X1t or X2t is best suited for your needs. X1t and X2t are for 1D and 2D modeling respectively. In these apps, you would set up your domain discretization and flow parameters. You can always check that the flow parameters are correct by setting an inert fluid (e.g. just Na+ and Cl-) and running the simulation. Once you have verified that these are correct, you can add the geochemical reactions that you have set up and tested in React. You can simply click and drag the Basis pane from React into the corresponding pane in the RTM app. There are a lot of resources available to help you get started with The GWB. The software is accompanied by six user guides which will explain various features. React is described extensively in the Geochemical Reaction Modeling User Guide. If this is the your first time using the GWB software suite, I would also recommend reviewing the SpecE8 section in the GWB Essentials User Guide, which explains how chemical mass distribution is figured. Usage of X1t and X2t are described in detail in the Reactive Transport Modeling User Guide. In addition to the user guides, there is also the GWB Academy, which offers a series of lessons on a wide variety of geochemical modeling topics. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Gregg, This error indicates that the unique GWB font used for GSS was not installed properly. Sometimes, reinstalling would resolve the issue. If that didn't resolve the issue, you can download the font and install directly on your machine. Please see our troubleshooting guide for step-by-step instructions. Best regards, Jia Wang Aqueous Solutions LLC

Hello Eva, The software works by iteratively solving numerical schemes to arrive at a solution and sometimes, certain variables can be better optimized to allow the software to achieve convergence. The default values are chosen to optimize computational effort and results for more scenarios. With your initial script (one without the gas fugacities), I was able to get your script to converge when I decreased your maximum step size, basically making the reaction progress take smaller steps. The default maximum step size is 0.01 and when I decreased it to half (0.005) and your script ran without issues. For controlling the step size in the GWB programs, see 6.22, delxi, in the GWB Command Reference. Alternatively, you can instead set a smaller initial step (dx_init) step, since the simulation has issues early on, but then return to regular steps later. Typically, the charge balancing ion is selected based on the highest uncertainty and concentration in your system. In this case, the initial fluid is very dilute and with the gas fugacities swapped in, the program is not able to solve for the initial equilibrium state while trying to maintain charge balance. When I turned off charge balancing your script ran without problems. In general, I suggest troubleshooting your scripts by doing a "go initial" run. This will test if your script will convergence on its initial composition without the complication of the reactants. In your input file with gases, the program was not able to speciate your initial fluid, so that was a helpful starting point. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, A few clarifications to follow up.. Please take a look at the Options dialog for extrapolate instead of the Stepping dialog. That was a mistake on my part. If you are using the Van't Hoff equation, please consult a standard thermodynamic text to check. If the dataset only has one equilibrium constant at 25C, the extrapolation will only hold the value constant at a different temperature. You can find more details regarding the extrapolate command for React and X1t in section 6.35 and 8.39 respectively. By the way, the dataset you attached have equilibrium constants for greenalite at principal temperatures up to 150C. Perhaps this not the dataset in your description? If you want to run a simulation with attached dataset at 80C, the GWB will perform an interpolation to internally calculate the equilibrium constant at 80C. Best regards, Jia

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