Jia Wang

Hello Arata, Thank you for posting your input files along with your surface and thermo datasets. I couldn't run your input files exactly as they are because of two surface datasets (SO4.sdat and Shimazui.sdat) I don't have. Here are some answers that I hope are helpful: 1. You are correct that the pickup command only retrieves the component concentration in moles. Typically in React, you would set the initial composition of your fluid (as the Basis) and then set a desired reaction path to alter your initial composition (e.g. titrating in reactants, sliding temperature, kinetic reactions, etc). You can use then use pickup feature as an easy way to set up the result from a simulation as a new starting point or as a set of reactants. It seems like you already have the starting composition of your experiment, since no reaction was prescribed to change the composition in your React simulation. In that case you can just use the same constraints as your Initial composition in X1t. If you would like to use React to create a new fluid composition for your starting point with the same volume as a node in your Reactive transport model, you can scale the bulk volume of your React simulation in the Medium pane to the same as one node volume in X1t. You can calculate the volume for one node from the Medium pane in X1t. For more information on configuring React reaction paths, please refer to section 3 Tracing reaction paths in the GWB Reaction Modeling User Guide. 2. Weight percent is the mass of mineral per mass solution times 100. Volume percent is the volume of mineral per system's bulk volume times 100. 3. In the React output text file, the sorbed concentration for each component is given in terms of milligram per kilogram solution. You can multiple the concentration by the solution mass given near the top of the output file to get the total mass sorbed. Alternatively, you can also render your result in Gtplot and change the unit to 'mg'. 4. Yes, the flow is set as volumetric discharge in GWB reactive transport applications. The unit is volume per cross sectional area per time. You can set the diffusion coefficient in the Medium tab in X1t. By default, the diffusion coefficient is set to 1e-6 cm/s. Please see section 3.3 Mass Transport in the Reactive Transport Modeling User Guide for more details. Best regards, Jia Wang Aqueous Solutions LLC

Hello L, You math looks correct to me. I am assuming that you're using 1000kg / m3 for the conversion from volume to mass. The GWB will display discharge in volume units, but you can most certainly do the conversion outside of the application. The model will also calculate the density of the solution as well if you would like to use that for your conversion. If you like, you can set up a very simple system in X2t to test your calculation. I think this may be a good exercise for you to familiarize yourself with the software before incorporating geochemical reactions. In a new X2t instance: set your discharge on the left boundary to 25 m/yr (Flow pane) your domain to the dimensions as you described above (Domain pane) add Na+ and Cl- as your solutes in the Initial pane and set small amounts of Na+ (e.g. 10 mmol/kg) and leave Cl- as the charge balancing ion. I just want to set some dilute fluid here that is basically non-reacting in Fluids pane, click add and if you configured the Initial pane, the fluid will copy over what you have included there. in the Intervals Pane, set the left boundary as the fluid you just added in the Fluids. Set simulation to end at 1 year go to the Run tab and select Go to trigger the calculation Once the run is finished, you can select Plot Results on the Results pane to render your run in Xtplot. You can display the result as a map of the 2D domain or examine the result for each row or column in the domain. You can plot the pore volume displaced along each time step of the simulation in either plot format. In a map plot, you would select the Variable type to map as Physical parameters and the Pore volume displaced as the variable. If you select the time level at the end of the simulation (1 year), you can see that the pore volume displaced is 0.025 everywhere in the domain. If you multiple the pore volume displaced by the total volume of the domain (0.025 * 2E6 m3), that would give 5E4 m3/year, your answer from above. You can play around with different variables to see how each affects the model outcome. You can find more details on configuring plots in Xtplot in Chapter 6 of the Reactive Transport Modeling User Guide. Additionally, I think you may also find the GWB Command Reference very helpful for learning about configurations in X2t and other GWB apps. Hope this helps, Jia

Hello Seyed, I couldn't replicate your exact output since I don't have your modified thermo database, but I was able to run your input file without the Mg++ component and Montmor-K. Setting fast reacting minerals as equilibrium reactions is a good strategy in geochemical modeling because the reaction proceeds to equilibrium so quickly that a kinetic description is not necessary. I suggest checking your longer simulation by shortening it so that it runs to completion and you can plot dissolution rates under Reactant Properties using Gtplot to see which mineral changes the most abruptly. I shortened your 20 year simulation to end on day 5 and saw that your have a relatively high rate of precipitation for pyrite initially, then goes to 0 very quickly as pyrite reaches saturation early on with respect to the system. I suspect that this was causing your simulation to take very small time steps. I suggest setting pyrite as a simple reactant to titrate into your system to see if that affects the result of your simulation relative to the kinetic approach. I would also recommend returning to your 2 day simulation and examine the rates for your mineral reactions as well to see if you can just use an equilibrium approach for any of these minerals. Please note that swapping a mineral into the basis pane sets the concentration of that component in equilibrium to that mineral, however, if you set the swapped mineral as a kinetic reactant, React would treat that mineral kinetically as your reaction path begins (i.e. sliding CO2 fugacity to 322.7). The porosity is calculated as the fluid volume divide by the bulk volume of the system. The bulk volume is composed of the mineral volume, fluid volume, and any inert volume that may be prescribed. So if your minerals dissolve, the total bulk volume will decrease and the porosity will increase. Running your model (without the input of Mg++ and Montmor-K), it seems like your total mineral volume decreases slightly and your fluid volume increased. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, The reactive transport model applications in the GWB carry flow in terms of specific discharge, which is also known as the volumetric flux. The volumetric flux is written in units of volume of fluid per area of your domain cross section per time. Because the units for volume are length cubed (cm^3) and area is length square (e.g. cm^2) , the simplification reduces the unit to length per time (e.g. cm/day). In the GWB, you can prescribe discharge as a constant value or allow the program to calculate it according to Darcy's law. In the latter option, you would have to provide the program with the hydraulic potential across the domain, permeability, and the fluid viscosity. For more information on how flow rate is carried in the software, please see section 3.2 Setting flow rate in the Reactive Transport Modeling Guide. If you would like even more information, please refer to Chapter 20, Transport in flowing groundwater, in the Geochemical and Biogeochemical Reaction Modeling textbook. The text provides a more detailed explanation on the theory and application of reactive transport modeling along with many examples setup in the GWB. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Jeremy, I am sorry to hear that you're having issues on your new Macbook. I suspect that the issue present is related to the M1 processor. Could you try closing all GWB apps and then rerun the installation as administrator? If that doesn't help to resolve the new issue on the new Macbook, I would suggest reinstalling on your previous computer for the time being. We are currently working towards a solution for compatibility issues on ARM systems. Best regards, Jia Wang Aqueous Solutions LLC

Hello Wen Qiu, I apologize for the confusion. The most current version is GWB 2021, release version 15.01. The thermo dataset downloaded from the GWB Academy will use the dataset format compatible in this latest version but not compatible with GWB 12.08. You can create a version that is compatible with GWB 12 by manually adding lactate to thermo.tdat and then saving it as a new thermo dataset. You can download GWB 12 formatted thermo datasets on the main GWB website or find them installed with the Gtdata folder. Hope this helps, Jia

Hello Wen Qiu, The thermo datasets available from the GWB Academy are updated to the latest format. If you are using an older version of GWB (GWB 2021 is the current release), your GWB applications are not able to read in the newer formatted dataset. You can open the thermo file with the error message in a text editor, locate the Lactate entry and then enter the corresponding reaction into thermo.tdat (a compatible version with the GWB software you have installed) and then save this new dataset with a different name. You can find the thermo datasets installed with the GWB in the Gtdata folder where the GWB is installed. For more information on using TEdit, please see section 9.2.2 Adding and deleting entries of the GWB Essentials User Guide. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, Simulation results in React are rendered in Gtplot. You can find ionic strength in Gtplot under the Variable type Chemical parameters. You can choose to plot ionic strength on the X or Y axis and then the sorbed fractions of various species on the other axis. For more details regarding Gtplot, please refer to section 6 in the GWB Reaction Modeling User Guide. Gtplot only renders result from one React simulation at a time. If you would like to plot results from multiple simulations on the same plot, you can export the numerical data from each and then generate the plot in Excel. Alternatively, you can create separate Gtplots and then overlay them in a graphics editing program. In the latter case, you would need to format the axes with the same range and intervals. Hope this helps, Jia

Hello, Act2 is used to calculate and plot Activity diagrams, which is a class of diagrams that show the stability of minerals and the predominance of aqueous species in chemical systems. An activity of a species is its effective concentration, given as the product of the concentration of species in molal times its activity coefficient. There is not a standard value for each species since the activity coefficient can vary depending on the condition of your system. If you have complete fluid analysis, you can use the SpecE8 application to calculate an activity of nitrate for your diagram in Act2. For more information on activity coefficients and model types, please refer to section 7 SpecE8 in the GWB Essentials guide. If you are interested in a more detailed explanation on activity coefficients, please see Chapter 8 Activity Coefficients in Craig Bethke's Geochemical and Biogeochemical Reaction Modeling text. You can also refer Chapter 5 of the GWB Essentials User Guide for more examples in Act2. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Emma, Most speciation diagrams like this are created in the React application, available in the GWB Standard and Professional packages. I am guessing that the user set a reaction path to titrate sulfate into your system and see how the concentration of Cu-complexes and free Cu(II) change over the course of the addition. By the way, if you set up a React simulation described above, you can directly generate the diagrams in Gtplot and don't need to render the diagram separately in Excel if you just want to plot in common concentration units (i.e. mmol/kg, molal, etc). If you would like more information on React titration paths, please look at section 3.1 Titration paths in the GWB Reaction Modeling User Guide. You can find this under the "Help" menu on any of the GWB applications or in the Docs pane of your GWB dashboard. If this is your first time using React, I would suggest reading through section 3 as a starting point. More information regarding Gtplot can be found in section 6 of the same user guide. If you aim to reproduce the diagram exactly, it would be very beneficial if you can find the input file that outputted the results used to make this diagram. Just an fyi, the pH speciation diagrams are a different type of reaction paths available in React. You can find more information regarding it in section 3.6 of the same user guide mentioned above. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, There is no option to select units when using the pickup command. Within the Basis and Reactants pane, the GWB does not provide a built in way to automatically convert between different units. You can, however, drag and drop the Results from a simulation into GSS and then use GSS to convert one or multiple units. For more information on this, please see section 1.7 Drag and drop feature in the GWB Essential User Guide. To see more details regarding the pickup feature, please see the GWB Command Reference. Best regards, Jia Wang Aqueous Solutions LLC

Hello Eden, You can certainly suppress minerals and species that you don't want the program to consider in the diagram. To do so, under the Config tab go to Suppress... Select the minerals and/or species you wish to suppress and hit Apply to save. On the Plot tab, your new plot should update to reflect your changes. Please refer to the GWB Command Reference for more details on commands available in the various GWB applications. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Julie, One of the new features added in GWB 2021 is the ability to convert datasets for the PhreeqC program to GWB thermo and surface datasets using the TEdit application. For more details on the conversion, please refer to section 9.3 Importing PhreeqC datasets of the GWB Essentials User Guide. You can also visit our TEdit webpage for examples on importing PhreeqC datasets. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello, You can use the GWB thermodynamic dataset editor, TEdit, to edit and add new reactions to a dataset. To get started, I recommend looking at section 9 Using TEdit in the GWB Essentials User Guide for examples and instruction on editing datasets. In particular, I think you'll find section 9.2.3 Adding and deleting entries and 9.2.4 Completing entries in thermo datasets very useful. If you would like further assistance with adding reactions to your dataset, please provide more details on the issues you're encountering and the dataset that you're working with. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Zixuan, You're welcome. I am glad to hear this fixed your issue. Best, Jia

Hello Eden, You're welcome. The reaction for H2(g) is written in terms of H2(aq) in thermo.tdat. Since H2(aq) is not defined in thermo_minteq.tdat, you would need to also copy over this reaction. You can either first copy over the entry H2(aq), or if you like, hold down the Ctrl key when selecting entries in thermo.tdat and select both H2(aq) and H2(g) to copy at the same time and then paste in thermo_minteq.tdat. To copy an entry in TEdit, you can right click on the entry on the tree structure in the left hand side panel and select copy or left click on the entry in the tree structure --> 'Edit' tab on the menu bar --> copy. In the dataset you want to paste the entry, go to Edit --> Paste. You can see an example of copying and pasting on our Thermodynamic dataset editor webpage. Hope this helps, Jia

Hello Zixuan, You do not need to refit your Log Ks after changing the capacitance values. You can set independent capacitances for each sorbing surface and load both into your React simulation. They do not need to be different surface models. In order to load both triple layer surface datasets, they must have a unique "Type" set. This is different from the "Surface Model" setting. I noticed in Kaolinite_P.sdat, the "Type" is set as 3Layer (find this in the header lines in a text file or Headers pane when opened in TEdit), which is the default setting in TEdit when you create a new surface dataset. If you had created a new surface dataset for Goethite as well and didn't change "Type" from its default setting, then React will only be able to load one of these datasets at a time. Please check that "Type" is unique between different surface datasets. I have included example dataset headers that can be loaded simultaneously: Dataset of surface reactions for gwb programs Dataset format: may20 Surface type: Kao Model type: three-layer Surface potential: n/a Surface capacitance: 0.70 0.20 … Dataset of surface reactions for gwb programs Dataset format: may20 Surface type: Goe Model type: three-layer Surface potential: n/a Surface capacitance: 1.10 0.50 Hope this helps, Jia

Hello Bea, You're welcome. You can only include a mineral in your basis by swapping it in for a component, which sets the mineral in equilibrium with that component. You can try swapping in Gypsum for SO4-- and run a Go initial calculation in React to see if the concentration of SO4-- calculated is close to what you fluid analysis indicates. If so, you can probably assume Gypsum is in equilibrium and swap it into your Basis. If you don't want to do that, or if your mineral is not in equilibrium in with your initial fluid, then it should be added as a reactant. It is not possible to include a mineral that doesn't constrain the initial fluid composition in the Basis pane. I am not sure that it is a good idea to use small arbitrary values for O2(aq) and H+. If you are receiving an error about setting O2(aq) concentration, then you are probably including reactions of species with various redox states. React will use the values set for O2(aq) to set the initial oxidation state and this will control the distribution of mass for all redox reactions unless they have been decoupled. Do you have any clues in your fluid analysis or environment that you can use to set the redox state of your system? Perhaps a HS- / SO4-- or another redox pair measurement? Is your fluid open to the atmosphere? If so, you may swap into the basis species on of these measurements to set the initial oxidation state. pH of a system is important too. Like any other component, the pH will affect the overall mass distribution of species that has H+ in its reaction. I am sorry to hear about the issues you're having with the update. Can you please attach an example input file and any custom thermo dataset so we can take a closer look? Also, what are the differences observed before the update and post update? Any details you can provide would be help us track down any issues. If you would like to revert to a previous version of the GWB for the time being, you can install the original installer for your software. Hope this helps, Jia

Hello Zixuan, You're welcome. I think the issue here may be that your two sorbing surface datasets doesn't have a Type identifier. When you create a new three-layer sorbing surface dataset, TEdit by default uses '3Layer' for a three-layer sorbing surface model as the 'Type'. This field has a couple of uses. The first is that it is used for defining properties of the surface, such as mobility_HFO, surface_potential, etc in the simulation. It is also used to prevent redundant surfaces, so each surface loaded requires a unique surface type. If both datasets have the Type field set to "3Layer", as you have in Kaolinite_P.sdat, then the program will load latest new dataset replace the current one. You can view and change the "Type" in the Headers pane if you open your dataset in TEdit or view it at the top of the text file if you open it in a text editor. Hope this helps, Jia

Hello Zixuan, To load multiple surface datasets, you can go to the Config tab -> Sorbing Surfaces... -> add and select the desired surface dataset. Hit "Ok" in the Sorbing Surfaces... dialog to save your changes. Best regards, Jia

Hello Bea, The Basis pane in React and other apps in the GWB is used to set the initial fluid composition. If you swap in a mineral in the basis pane for a component (e.g. Quartz for SiO2(aq), this would ask React to set the fluid in equilibrium with that mineral and calculate the dissolved concentration accordingly. You can also swap in a gas fugacity if that is assumed to constrain that component concentration in the fluid. If you want to react a mineral with a fluid, then you should set the mineral as a reactant instead. If you swap in a mineral for O2(aq) and H+, React will calculate the concentration of dissolved O2(aq) and H+ component in equilibrium with the minerals respectively. You can set the initial oxidation state of your fluid by swapping in the redox species for the O2(aq) component and then add the basis species component concentration. For example, I can set the oxidation state of a fluid in the basis pane by swapping in Fe3+ for O2(aq), add in Fe++, and set the concentration for both. The software will calculate the Eh for the overall system based on Fe3+/Fe2+ component concentrations. You can also swap in a mineral for O2(aq) as well to set the oxidation state. Note that the initial oxidation state and pH is not fixed throughout the simulation unless you choose to do so specifically in the Reactants pane. Reactants times is a factor the program multiples the mass of reactants set to react into the system. For example, if you set 100 milligrams of Quartz with reactants times 2, then the program will react a total of 200 milligrams of Quartz into the system. Delxi is used to set the reaction interval the maximum length of the reaction program over the course of the simulation. By default, this is set at 0.01 so that the program takes 100 steps throughout the simulation 0.01, 0.02, 0.03.. etc. There are two other commands that control the output of the simulation results to the output text file and Gtplot. Please see the GWB Command Reference for more information on these settings. You can add minerals to your system through the Reactants pane as a simple reactant or as a kinetic reactant. This depends on the type of reaction that you are trying to model for gypsum in your system. Is gypsum reacting quickly in your system over the time scale that you're interested in? If so, then you might consider adding it as a simple reactant that simply dissolves or precipitates according to thermodynamics. If gypsum is reacting slowly, then you might consider a kinetic approach. If it barely reacts at all, then you might consider ignoring it. To see more on how to add various types of reactants, please see section 3 Tracing Reaction Paths and 4 Kinetic Reaction Paths in the GWB Reaction Modeling user guide. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Andrew, I believe most commercial labs would typically report ppm units as mg of solute per kg of solution. If your analysis specifies concentration units in mg of solute per kg solvent, you can convert to molal using the appropriate mole weight as described above. For dilute solutions, the mass of solvent water is approximately the solution mass, so the mass of solute per mass of solution is close to the mass of solute per mass solvent. Hope this helps, Jia

Hello, Activity diagrams require user to input the relevant activities or fugacities of species. The program uses a simple method to draw equilibrium lines and calculate stability fields. If you have a fluid analysis, you can 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. You may also be interested in the Phase2 application as well. Unlike Act2 and Tact, Phase2 requires the user to set up an initial system and prescribe reaction paths in the x and y axis. The program then solves the solution to a multi-component chemical system at each node numerically and assembles the result in a grid form. If you're interested in Phase2, please refer to chapter 7 of the Reaction Modeling User Guide for more information and examples. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Christophe, You can overlay data points from a GSS spreadsheet to an Act2 diagram. You would first need to prepare a GSS file that contains the axis variables on your diagram, in this case, Eh and pH. Save the GSS file. In Act2, create your diagram and go to File --> Open --> Scatter Data... --> select the GSS file your had prepared. After you hit Ok or Apply in the Scatter Data dialog, Act2 will read the data points and project them onto the diagram. For more information and example on how to use scatter data, refer to section 5.6 Scatter data in the GWB Essentials User Guide. Hope this helps, Jia Wang Aqueous Solutions LLC

Hello Tanya, Yes, the bulk concentration for HCO3- is specified for the sum of aqueous species and carbonate minerals (if supersaturated). The speciation calculation does not distribute mass to the gas phase but instead will calculate fugacity of that gas in equilibrium with the fluid. Best regards, Jia