katezat

Hello Qianwei, You can use TEdit, the graphical thermo data editor, to see which dataset may be appropriate for your work. To load a given dataset into the GWB program go to File -> Open -> Thermo Data… If there’s a species that’s not included in one dataset, you can easily copy a species from one dataset to another, or add data from the literature. For more information, see the TEdit section in the GWB Essentials Guide. You can also view tutorials on how to edit thermo datasets here. Kind regards, Katelyn

Hello Guillermo, Can you please try attaching your thermo data file (.tdat) and your Act2 file (.ac2). The forum only allows certain file extensions. Thank you, Katelyn

Hi John, Yes, a 2 day residence time is a fair interpretation. I think you understand the concept, but perhaps you misstated your question? To increase the residence time you would want to decrease the value of “reactant times” or increase your model run time. If you wanted a residence time of 4 days, for example, you could displace the pore fluid only 5 times (reactants times = 5) in 20 days. Alternatively, you could displace the original fluid 10 times like before but increase the time span to 40 days. Please keep in mind that while the “residence time” is equivalent in either case, the results would not be equivalent. Kind regards, Katelyn Aqueous Solutions LLC

Hello Yousef, There’s no KI mineral in any of the thermodynamic datasets installed with the software but you can easily add a new mineral to a thermo dataset. To do so, you’ll need an equilibrium constant corresponding to a reaction to form the mineral from species in the dataset (eg. KI = K+ + I-). You would need at least two log K’s at 25°C and 60°C (assuming you’re working with the default dataset – thermo.tdat, which uses those default temperatures) to work at 50°C, and the more data you have the better. You can use the TEdit program (under the support tab on the GWB dashboard) to modify a dataset in this way. It’s always a good idea to start by opening an existing dataset and saving it to a different name before modifying it in some way. For more information, see the TEdit section in the GWB Essentials Guide (you can access PDFs of the user's guides from the Help menu of any GWB program, or from the Docs pane of the GWB dashboard). You can also view tutorials on how to edit thermo datasets here. The GWB programs operate within the temperature range of the thermo dataset currently loaded. The default thermodynamic dataset thermo.dat contains log K entries compiled along the steam saturation curve from 0°C to 300°C. You can use a thermo dataset compiled at the pressure of interest, but hydrothermal chemists not uncommonly assume the effects of confining pressure are small compared to the uncertainty in determining log Ks and activity coefficients. Note, however, that gas partial pressures are almost invariably significant. You account for the partial pressure of a coexisting gas by setting its fugacity. Before you find the KI thermo data, you can take look at halite solubility using SpecE8. Add Na+ and Cl- ions to your initial system and swap halite in for one and constrain it with an arbitrary mass. You can set the other entry as a charge balancing ion. Set your temperature of interest and run your model. For more information, see Using SpecE8 in the GWB Essentials Guide. Kind regards, Katelyn Aqueous Solutions LLC

Hello Juan, If you’d like GSS to read in Mexican regulatory water standards you can create a new water quality file, or it might be easiest to modify the existing dataset and save it to a different name (ex. MexicoWaterQualityRegs.dat). You can open the file from the directory as you mentioned, and modify it using a simple text editor like Notepad (right click on the file->Edit with Notepad). Once you have completed your modifications, you can load your new water quality file into GSS by going to File -> Open. To set your modified water quality file to be the new default go to File -> Preferences… For more information, see section 3.4 Regulations, replicates, standards, and mixing in the GWB Essentials Guide (you can access PDFs of the user's guides from the Help menu of any GWB program, or from the Docs pane of the GWB dashboard). Kind regards, Katelyn

Hello, You should search the literature for published datasets with information on mercury-sulfide species. I noticed one of our other users was looking at mercury species and shared the link to a USGS report: http://pubs.usgs.gov/pp/0713/report.pdf. The paper includes some information on mercury-sulfide species at 25 C, but it should help to get you started and may include some useful literature references. After you’ve collected the necessary thermodynamic data you can use TEdit to quickly and easily modify an existing thermo dataset. You can find some tutorials on how to edit thermos datasets here and for more information, see section 9.1 Getting started with TEdit in the GWB Essentials Guide. Kind regards, Katelyn Aqueous Solutions LLC

Hello Yousef, If you'd like to move your license to another computer, you can easily do so by returning to the GWB Activation Utility (under the Support pane of the GWB dashboard), select your activation code, and then click Deactive. After the status changes to "not activated," you can activate the software on another machine. Please let me know if you have trouble. Kind regards, Katelyn Aqueous Solutions LLC

Hello John, Thank you for providing additional details about your model. It sounds like what you're trying to do is very similar to the "flush" model that is already build into GWB Standard. A flush model tracks the evolution of a system (rock grains and pore fluid) through which the fluid migrates. At each step in the model, an increment of unreacted fluid passes into the system, displacing an equal mass of the existing pore fluid. You can set minerals in the usual way to begin at equilibrium and then react kinetically over the course of the simulation. You can displace the system’s pore fluid any number of times. Section 3.3 of the GWB Reaction Modeling guide shows how to set up a flush model. Chapter 2 in the Geochemical and Biogeochemical Reaction Modeling text discusses the local equilibrium models in further detail, beginning in Section 2.1 and then fleshing out the ideas more mathematically in Section 13.2. There are at least a couple of examples of flush models later in the book: dolomitization (Section 19.4) and alkali flooding (30.2). The primary difference between a flush model and the simulation you describe is that a flush model is continuous, rather than proceeding stepwise. Such configuration is generally preferred to a discrete simulation. If you have your heart set on a stepwise series of simulations, I can look into it, but I’m pretty sure it will take a lot more effort than a flush model, while yielding essentially the same results. Kind regards, Katelyn Zatwarnicki Aqueous Solutions LLC

Hello Tanzil, You can easily modify thermodynamic datasets in the GWB using TEdit (under the support tab on the GWB dashboard). It's always a good idea to start by opening an existing dataset and saving it to a different name before modifying it. For more information, see the TEdit section in the GWB Essentials Guide (you can access PDFs of the user's guides from the Help menu of any GWB program, or from the Docs pane of the GWB dashboard). You can also view tutorials on how to edit thermo datasets here. Once you have completed your thermo dataset you can load it into Act2, go to File ->Open->Thermo Data... (or Ctl+T) to select the thermo dataset you would like the program to reference. Kind regards, Katelyn Aqueous Solutions LLC

Hello Dhanamadhavan, I'm sorry to hear your computer hard drive was corrupted. I have manually reset your activation code and you should now be able to activate your GWB Student license again. Please let me know if you have any trouble. Kind regards, Katelyn

Hi Claudia, I’m a little confused. Can you clarify what species you need that aren’t in the default thermo dataset? Please be sure to include the correct formula and charge for each species. SiO2 is the basis species for Si in thermo.tdat, while H4SiO4 is the basis species in thermo_minteq.tdat. They are essentially the same in that they both represent uncharged Si, but H4SiO4 has two water molecules included in the formula. Both datasets included the deprotonated species H3SiO4- and H2SiO4(2-) which you were trying to add, so I don’t think you need to modify the default dataset at all. Since thermo.tdat already has UO2++ as a redox species, I don’t see the need to add it again as a basis species, or to change it to a basis species in the thermo dataset. When you construct your model, simply decouple the UO2++ from the U++++ basis species. That way, UO2++ is treated as a basis species and is thus independent from U++++. To decouple the redox pair go to Config > Redox Couples and select UO2++/U++++. You can read more on Redox couples in Section 7.3 (Redox disequilibrium) in the GWB Essentials Modeling Guide. For even more information on Redox disequilibrium take a look at Chapter 7 in the Geochemical and Biogeochemical Reaction Modeling text. Kind regards, Katelyn Aqueous Solutions

Hello Claudia, I believe the error message you are encountering is related to the default setting to display water limits. The water limits refer to the conditions under which water becomes so oxidizing that it is unstable and breaks down to O2(g), or where it is so reducing that it forms H2(g). Normally you’ll see two dashed lines for the upper and lower water stability limits on an Eh-pH diagram. Act2 by default will only plot species within the water limits, but not outside them. You encounter the error because thermo_minteq.tdat does not include a reaction for the H2(g) species, so it can’t draw the line. You can tell the program to ignore the water stability limits (and prevent the error you’re seeing) by right-clicking on the plot, clicking View…, then unchecking water limits. For more information, see section 3.64 water limits in the GWB Reference Manual. When you open the Suppress dialogue you can change the “list” pulldown to include all species, or only the aqueous species, minerals or gases. If you know a specific species’ name, you can begin typing it to find it more easily. Sometimes it’s helpful to suppress all species, then to unsuppress those that you’d like to include in your diagram. You can also use the “select with...” pulldown to highlight all the species containing a certain basis entry. The “invert selection” button may come in handy. With it, you can unselect what was highlighted before and automatically select species that were not previously highlighted. You can also hold down the Ctrl key and left click to select multiple species or highlight a selection by holding down the Shift key to select adjacent species. Kind regards, Katelyn

Hello, To find out what thermo database you are using currently, go to the File... menu and select File Properties->Thermo data. This will bring up a dialog box with information on the current thermo database. The default thermodynamic dataset used in The GWB is thermo.tdat. You can find more information on the different thermo datasets distributed with the software here. Thermo datasets are fully editable. To add a new mineral, for example, you just need an equilibrium constant corresponding to a reaction to form the mineral from species in the dataset. You can use the TEdit program (under the support tab on the GWB dashboard) to modify a dataset in this way. It’s always a good idea to start by opening an existing dataset and saving it to a different name before modifying it in some way. For more information, see the TEdit section in the GWB Essentials Guide. You can also view tutorials on how to edit thermo datasets here. Kind regards, Katelyn

Hello Claudia, The error message you’re encountering is due to the fact that you haven’t set up your plot axes in Act2. Before you can open the reaction trace “.gtp” file in Act2, you’ll need to set up your activity diagram x and y axes and make sure your reaction path model contains information that matches the axes of your diagram. For example, if you wanted to overlay a reaction trace on an Eh-pH diagram, your reaction path model must contain information on the oxidation state and pH. Be sure to use the same thermo dataset in both Act2 and React and make sure the relevant species match. For example, if you swap HCO3- for CO3-- in React you should do the same in Act2. For more information, see Sections 5.5 Reaction traces or 6.5 Reaction traces and scatter plots in the GWB Essentials Guide. Kind regards, Katelyn

Hello Kaushik, To clarify, you should use (not edit) the default thermo.tdat dataset for now. As far as ready-to-go datasets that come with the GWB, you will need to use a Debye-Huckel based thermo dataset, because there is no virial model dataset which contains iron. Of all the Debye-Huckel based methods, the B-dot (which thermo.tdat uses) is the best at higher ionic strength. However, as you mentioned be mindful as there is error involved. If you take a look at those references, you can find the information you will need (virial coefficients and information needed to calculate equilibrium constants). Kind regards, Katelyn

Hello Kaushik, I’m glad to hear you’re enjoying the free student version and demoing our Professional package. There are a few ways you can modify the amounts of water or rock in your system. If you just want to change the amount of water in your system you can simply modify the mass on the Basis pane (1kg -->10kg). If you need to change the amount of any mineral reacted into the fluid, you can do so for each individual mineral on the Reactants pane. Or, if the proportions of each mineral will remain the same, you can simply adjust the “reactant times” value. It’s a multiplier (default 1) for the mass of any reactant on the Reactants pane, whether it’s solvent water, species, minerals, or gases. Let’s look at a fluid mixing example. If you have 1 kg solvent plus some dissolved solutes in your initial system (the Basis pane) and 1 kg solvent plus some solutes in the Reactants pane and set the "reactants times" to 1 you will end up with 2 kg solvent plus some dissolved solutes in the mixture. If you change the “reactant times” to 2 you will end up with 3kg solvent plus some dissolved solutes in the mixture. It sounds like you’ve configured the minerals in basalt as simple reactants to be added to the fluid. This is what we call a titration model. Basically, you start with a fluid (or fluid-rock equilibrium system), to which the model reacts a small amount of the reactant minerals at a time, taking a number of steps to add the entire reactant mass. So, if you plot some value vs. the variable “mass reacted”, you’ll see how your system evolves after each incremental addition of the minerals making up basalt to the fluid. A reaction path model, then, is not just about the final result. There is information available at each step of the process. Maybe this is all you need? Take a look at section 2.2.2 Titration Models in the Geochemical and Biogeochemical Reaction Modeling text to see if this setup is appropriate. React can model alternate configurations, as described in Chapter 13, that may be more appropriate. Kind regards, Katelyn

Hello, You can easily edit your Act2 diagrams in PowerPoint or Adobe Illustrator in a few steps. To plot varying activities of silver on one diagram, you'll need to export a diagram for each different activity. To export your plot, select Edit>Copy As>Enhanced Metafile. Open up Microsoft Powerpoint select Paste. Select Arrange>Ungroup>"Yes" convert to Microsoft Office drawing object. Then you can move labels, select individual lines to change the color or thickness. To assemble multiple diagrams, I would add each diagram to a new slide and copy the lines you need. Be sure you don't move the plot or adjust the size to maintain the proper scale. We also have a tutorial to show you how to overlay diagrams on our website under Using GWB "How do I overlay my diagrams." Kind regards, Katelyn

Hello Kaushik, It would be best for you to modify the default thermo.tdat dataset. You should search literature for published datasets similar to Harvie-Moller-Weare model (Harvie and Weare, 1980)( Harvie et al.,1984). More recent publications might contain data on iron species. Hope this helps, Katelyn

Hello Kaushik, Minerals plotted on an Eh-pH diagram are saturated under those specific oxidation and pH conditions. However, I wouldn’t recommend using an Eh-pH diagram to get information on mineral saturation. If you are interested in calculating the saturation index for minerals in your samples, you can easily calculate it using GSS (click +analyte > Calculate… > Variable type: Mineral saturation). I’m not exactly sure what you mean, but there is no automated way to produce a large number of Eh-pH diagrams. Do your samples differ very much? I don’t think you would find it very meaningful to make multiple slightly different Eh-pH diagrams. Instead, you might want to create one representative Eh-pH diagram for your data and plot your other samples as scatter data on the diagram. You can take a look at Section 3.6.5 Scatter data in the GWB Essentials Guide to learn how to plot GSS data on diagrams. Kind regards, Katelyn

Hello Kaushik, 1) When you select species to diagram in Act2, you need to enter the activity not concentration values. In dilute solutions, it is sometimes safe to assume the activity is equivalent to molality. In fact, this is likely what you assumed when you learned to make activity diagrams by hand. If that assumption is not valid for your system, you can use GSS or SpecE8 to calculate the activity of individual species in solution. You just need to pick an appropriate pH and oxidation state as constraints. You can read more about calculating the activity of free species in the GWB Essentials Guide GSS and SpecE8 chapters. 2) You are correct, aqueous species are colored blue and mineral species are yellow. In real systems it’s very possible to have complex aqueous species like FeSO4+ or FeSO4; not all species are completely dissociated. Consider a strong acid like HCl. It will almost completely dissociate to H+ and Cl-, but there is still a small amount of the HCl complex at most pH values (and if the pH is low enough, you’ll have more HCl than H+ or Cl-). A weak acid like carbonic acid (H2CO3) will dissociate to an even lesser extent, so you can find different complexes such as H2CO3, HCO3-, CO3--or CO2 all in solution. In natural systems, it’s very common to find free species and complexes in solution. Typically the higher the ionic strength, the more complex species you’ll find. For more info, take a look at section 6.3 Red Sea Brine in the Geochemical and Biogeochemical Reaction Modeling text. Pay close attention to the comparison between complexing in three different waters: Amazon River, Seawater, and Red Sea brine. Kind regards, Katelyn

Hello Kaushik, An activity diagram is a simple representation of a chemical system. It shows the predominant form of the main (diagram) species as a function of two variables (Eh and pH in your case), optionally accounting for complexation with additional ligand species. When K+ is the main species, everything that plots on the diagram must include potassium. When SO4(2-) is the main species, everything that plots must include sulfur. When Fe++ is the main species, everything that plots must include iron. It is possible for a mineral like Jarosite, which contains potassium, sulfur, and iron, to plot on a diagram with any of the above-mentioned species as the main species, but it won’t unless it is the predominant form under the conditions of the diagram. Jarosite is a stable mineral phase when you diagram K+ or SO4(2-) but not one of the most stable mineral phase for iron. In any activity diagram, you can suppress a species to allow the next most stable species to form in its place. If you want Jarosite to plot on your diagram with Fe++, you will need to suppress (config> suppress) some stable species. Kind regards, Katelyn

Hello Isaiah, This seems to be a question for someone with specific knowledge of soil chemistry rather than knowledge of the GWB. I waited in hopes another member could offer some insight to your question since I don’t know the answer. I will tell you that you can account for sorption of aqueous species onto surfaces by several methods, including the two layer surface complexation model (including the constant capacitance and constant potential models), ion exchange, distribution coefficients (Kd’s), Freundlich isotherms, and Langmuir isotherms. In each case, you supply a dataset describing the surface chemistry. Templates for each of the surface types are installed with the software and you can read more on sorbing surfaces in the Essentials Guide, Section 2.5 Sorption onto mineral surfaces. Hope this helps, Katelyn

Hello Kelly, The water type calculation shows the most abundant cation and anion in a sample, based on concentrations in meq/kg fluid. Keep in mind this is referring to the actual aqueous species, calculated after the sample is speciated. To understand this calculation better, try launching SpecE8 for any one or more of your samples. To do so, in GSS >Analysis> Launch....select your sample(s). View the results from SpecE8 to see the most abundant cation and anion (under aqueous species) for your speciated sample. Even though your input meq/L concentration for Ca++ was greater than Na+, the speciation results show Na+ as the predominant free cation. Kind regards, Katelyn

Hello Tomas, There are quite a few ways you can create speciation vs. pH plots. The easiest method is to set up a reaction path model and slide the pH (vary the pH from 2 to 12) using the GWB program React which is included in our Standard package. Check out example 3.6 in the Reaction Modeling Guide (you can access PDFs of the user’s guides from the Help menu of any GWB program, or from the Docs pane of the GWB dashboard). log ug/kg U++++ = -5 Na+ = .2 molal balance on Cl pH= 2 slide pH to 12 In the free GWB Student Edition, you can’t create reaction paths but you can create the plots in steps using SpecE8. To do this, setup an equilibrium model for your fluid and run the model at one pH and export the numerical results to excel. You can repeat the runs varying the pH values and exporting the results each time. log ug/kg U++++ = -5 Na+ = .2 molal balance on Cl pH= 2 go pH=3 go Alternatively, you calculate the concentration of uranyl complexes in GSS directly. You can enter a sample in GSS the same way you define a fluid in SpecE8 or React. If you copy your sample multiple times and change the pH for each, you can calculate uranyl species concentrations for all of your sample entries by selecting + analyte> Calculate... GSS sends the data entered in your spreadsheet to SpecE8 calculates the species concentration values and displays the value back in your GSS file. To graph your GSS data select Graphs> XY plot to view a plot of your data in Gtplot. To add the balance on Cl- command in GSS go to: Data>Constraints> Trailer commands If you are interested in upgrading to our Standard package you or your advisor may be eligible for an academic discount on a purchase of a new license. Please visit http://gwb.com/requests.php to request a quote. Kind regards, Katelyn

Hello Mark, Can you please explain how you are calculating your g/kg to mol/l unit conversion? What values do you think you should get and what values are calculated using GSS? Please attach your GSS and SpecE8 files so we can take a better look at your problem. In any modeling exercise, there is often some difference between values calculated from a model and those determined directly. You can find information on calculating the activity of water using the B-dot model and virial methods in Chapter 8 of the Geochemical and Biogeochemical Reaction Modeling text. Kind regards, Katelyn