Brian Farrell

Hi, SpecE8 should launch with whatever thermo dataset is loaded into GSS. If you want to use thermo.com.V8.R6+.tdat in both, your best bet is to load it into GSS first (File - Open - Thermo Data - thermo.com.V8.R6+.tdat). If you're content with GSS using thermo.tdat but you want SpecE8 to launch with the expanded dataset, you could enter the trailer command "data thermo.com.V8.R6+.tdat" in GSS's Launch dialog (you don't actually include the " and "). See section 3.5, Launching SpecE8 and React, in the GWB Essentials Guide for detailed information on the Launch feature. Section 5, SpecE8 commands, in the GWB Reference Manual contains the list of commands that you can tell GSS to pass along to SpecE8 when it launches. And you can always go to File - File Properties - Thermo Data to see what dataset is currently loaded into a GWB program. File - View will allow you to see the contents of that dataset. As for the "hanging" problem you're experiencing, is it during or immediately after the launch of SpecE8? Or perhaps after it's launched and you've changed the thermo dataset? What GWB release are you using? Can you attach the script you're using? Plot output files (like SpecE8_plot.gtp) contain information about the activity model used (broad Debye-Huckel-based methods vs. HMW type) and you can see this at the top of the Gtplot window, but there is nothing in the printed text output file (SpecE8_output.txt) about the activity model, and nothing easily accessible in either about the thermo dataset used (you can go to Config - Output in SpecE8, change the plot dataset format from binary to text, then after running you can right-click on the plot file and select Edit to see this info). I'm not sure what you mean by the simulation running when you open SpecE8 output, unless you're actually referring to the SpecE8 input file (.sp8 extension) that is generated by GSS. This will always open exactly as it was when GSS created it, unless you save over this file after changing the thermo dataset. As I mentioned above, though, I think your best bet is to change the thermo dataset from the start in GSS. Hope this helps, Brian Farrell Aqueous Solutions LLC

Hi Maki, I'm glad to hear that 10.0.9 is faster for you. We've just come out today with another maintenance release, 10.0.10. Please update to that release and if you encounter any problems with slowness take a screenshot of your GWB Activation Utility and send it to support@gwb.com. Regards, Brian

Dear GWB users, We are pleased to announce our latest GWB10 maintenance release, GWB 10.0.10. The 10.0.10 update fixes a glitch in the isotopes dialog; resolves a problem in Act2 and Tact when more than one speciating ion does not speciate; corrects a problem reading the sixth coefficient in the temperature expansion of beta2 from HMW datasets; and fixes all known issues. Update from 10.0 - 10.0.9 at no charge to ensure you have all the newest features and bug fixes. Existing installations should automatically update to this release, unless auto-update is disabled. In that case, users should update their installations from the Support tab of the GWB dashboard. Regards, Brian Farrell Aqueous Solutions

Hi syed, The Geochemist’s Workbench is at its core a thermodynamic modeling program that solves mass balance and mass action equations. The “zero” values you’ve specified for the component concentrations don’t work with these. The program can, however, handle very small numbers (for example, 1e-9 mmol/kg) which you can use in place of the “zero” values. For more information, please see section 7.2, Equilibrium models, in the GWB Essentials Guide. By the way, it’s a good idea to start with some simple calculations in SpecE8 or React before you set up a reactive transport model. You could start, for example, by equilibrating your inlet fluid in SpecE8 to understand its composition, then moving on to the initial fluid, or the initial fluid and rock system. You may find that it's necessary to change the charge balancing ion, as described in the section referenced above. Hope this helps, Brian Farrell Aqueous Solutions LLC

Hi Maki, Thank you for the clarification. I spoke with a programmer about your questions. He would like a little more information. Where are you trying to save your input files? Are you trying to save to a protected folder? As far as I can tell it has always been necessary to specify a file name when using the File - Save As option in the GUI or the "save" command on the Command pane. Regarding the slowness in 10.0.8, is a new instance of a program like React slow to open from the Dashboard? Or is it only slow when you're trying to open a saved React script? Can you please install the latest release and send us a screenshot of the GWB Activation Utility if the program is still slow? Finally, do you have the "Show Announcements" checkbox selected on the Settings pane of the GWB dashboard? If so, does unchecking it make the GWB programs any faster to load? Thanks for your help. Regards, Brian

Hi Maki, I don't understand the issue that you're having. Are you trying to save input files for any of the GWB programs (Rxn, Act2, SpecE8, etc.)? Or one program in particular? Or by script files are you referring to script files written in the Basic language for use with the Custom Rate Law or Heterogeneity features? Have you experienced this problem during the entire time you've been running 10.0.6? Or has the problem only arisen recently? Can you please tell me what Windows OS you're using, whether you're running the 64 bit or 32 bit installer, and any other details that may be important? Maintenance release 10.0.6 fixed some issues with sluggish plotting that existed in the previous release, but we're not aware of any problems with the programs opening or operating slowly in subsequent releases. Can you give us any more information? Is the dashboard slow to open, or only the individual programs? In general, it's most helpful to report these issues when you first notice them, rather than installing an older version without notifying us. Regards, Brian Farrell Aqueous Solutions LLC

Glad to hear you've got it figured out. Cheers, Brian

Hi Andrew, I'm glad to hear that you're making progress. Regarding the phrase "RETURN rate", the script needs to return some value for the reaction rate which is done with the return statement. Your React simulation will likely still run without the RETURN statement, but the reaction rate will just be zero over the entirety of the reaction path. You can take a look at the Kinetic parameter "_ dissolution rate" in Gtplot to verify this. Regards, Brian

Hello again, I'm not sure whether you're trying to go with part of the approach described in your first post. You cannot, with knowledge only of delG0f at 25 C, simply plug in a different temperature into the equation log K = -delG0-reaction/2.303*R*T (you had delG0-f in your first post) to get the log K at that temperature. You would need to know delGo-reaction for every temperature at which you want the log K. For more information, please see a reference like section 9.6, Change of K with temperature I, in Greg Anderson's Thermodynamics of Natural Systems. Regards, Brian

Hi, I think you're on the right track now. The delG0f's are properties of individual species, while the delG0-reaction depends on the stoichiometry of the reaction written between those species. The log K also depends on the reaction, not the individual species, so you need to figure out the delG0-reaction (as described in your second post) before you can calculate the log K for the reaction. Hope this helps, Brian Farrell Aqueous Solutions LLC

Hi, After checking out your input file I went to the Reactants pane, clicked the "+" next to "script", then clicked "Edit..." to open up the script dialog. After deleting the first ( kinetic Anorthite rate_law = { ) and last ( } ) lines I'm able to start running your model. FYI, you'd use commands like that if working from the command pane, but not when using the GUI. Try opening the two attached input files and comparing the command input (go to the Command pane) with the GUI input (go to the Reactants pane the above-mentioned rate law dialog). The model does fail pretty early in the calculation, though. I played around a bit and one of a couple different changes let the model run to completion. Decreasing the timescale quite a bit worked, and so did setting a pH buffer (on the Reactants pane, click add - fixed - pH). Do either of these changes seem reasonable? Are the pre-exponential factor and other terms that you entered all correct? Regards, Brian anorthite dissolution_Alt1.rea anorthite dissolution_Alt2.rea

Dear GWB users, You can take part in our Geochemical Reaction Modeling workshop for only 4900 ZAR when you register for the 35th International Geological Congress in Cape Town this year! (4900 Rand is about $350, or €330.) The August 27-28 workshop immediately precedes the IGC. You need only add the workshop to your online registration. You can also join the workshop for 5900 ZAR, if you don't plan to attend the Conference. Join the fun and be sure to leave a few days to explore Cape Town and South Africa's amazing Western Cape. Details are on our Cape Town workshop page. Don't miss out: the registration deadline for IGC workshops is June 30, 2016. Regards, Brian Farrell Aqueous Solutions LLC

Hi Sebastian, If your instrument provides elemental concentrations, then you would want to add SO4-- as S, and HS- as S. GSS uses SpecE8 to perform its calculations, so you can give GSS any command that SpecE8 would accept as a "trailer command". The GWB Reference Manual includes all of the commands that all the GWB programs, including SpecE8, accept. You can also go to the Run - History dialog in SpecE8 to see the command that is equivalent to every click that you make on the GUI. In your case, you'll want to swap H2(aq) for O2(aq), like you do in SpecE8, then set its concentration. Just go to Data - Constraints to add the trailer command. For more info, please see 3.2.5, Calculating analytes, and 3.5, Launching SpecE8 and React, in the GWB Essentials Modeling Guide. Hope this helps, Brian

Hi, You'll start out as you would if you were to use the GWB's built-in rate law. On the Reactants pane, click "add" - Kinetic - Mineral... and select labradorite from the pulldown. Then, change the pulldown next to "rate law" from "built in" to one of the options for custom rate laws, like "script file". In that case, you write your rate law script in the BASIC language. You'll need to define your custom variables (like R, n, and KT) within your script, but some of the parameters that are used in the built in rate law, like rate constant, can be specified within the GUI if you'd like. You can access any of the "internal parameters" in Table 5.1 of the GWB Reaction Modeling Guide in your rate law. Examples include the temperature (TK for Kelvin, TC for Celcius), rate constant that you defined (rate_con), current pH (pH), etc. You can also access a variety of "helper functions" that are found in Table 5.2 of that same guide. For example, activity("H+") or activity("Al+++"). For the temperature-dependent formation complex constant, KT, I would set the value directly at first, then once you're comfortable with the rate law you could set up a polynomial equation within your script to evaluate KT as a function of temperature. For more details and examples, please take a look at section 5, Custom Rate Laws, in the GWB Reaction Modeling Guide. Hope this helps, Brian Farrell Aqueous Solutions LLC

Hello, Congratulations on getting to the point where you're ready to publish your data. You can certainly use any plots or calculations that you made with the GWB Student Edition in your thesis. Please cite either Craig Bethke's Geochemical and Biogeochemical Reaction Modeling text, the GWB Student Edition website (student.gwb.com), or both. FYI, GWB Release 11 is now available. As a GWB Student Edition user, you have access to the latest release. Go to the Upgrade pane of the GWB dashboard to find the GWB11 installer. Regards, Brian Farrell Aqueous Solutions LLC

Dear GWB users, Sign up for our famous Reactive Transport Modeling workshop in super-fun, surprisingly affordable Yokohama for only ¥13400 — about €110, or US$120 — when you register for the Goldschmidt 2016 conference! The workshop takes place June 25-26, immediately preceding the Goldschmidt. Simply add the Reactive Transport Modeling workshop to your cart when you register, or return anytime and add it to your purchases. Please see our Yokohama workshop page for more details. Workshop registration ends May 26, 2016, so don't delay! Regards, Brian Farrell Aqueous Solutions LLC

Hi Sebastian, You can use a thermo dataset compiled at the pressure of interest, but you can’t specify a confining pressure within your model that deviates from what’s in the database. It’s common to 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. I’m not exactly sure what you’re doing, but I’d like to clarify that the “as” options within GSS, SpecE8, and the other apps refer to how you’d like to constrain the amount of some component. The mole weights of HS-, H2S, and S are all different, so 1 mg of HS- is not the same as 1 mg of H2S or S. Your analytical instrument could report a concentration in terms of either of the species or in terms of the amount of the element itself, so you use the “as” option to set up your input correctly. Please see section 3.1, Your first data sheet, and 7.1, Example calculation, in the GWB Essentials Guide for more info. You need to disable redox coupling reactions to treat separate oxidation states as independent components within your model. By adding both a basis species (SO4--) and a redox species (HS-) to your spreadsheet in GSS, the HS-/ SO4—redox pair is automatically disabled (check the Data – Redox Couples dialog to confirm). SpecE8 behaves slightly differently in that you need to decouple the pair (Config – Redox couples) before you add the redox species (HS-) to your basis. Please see section 2.4, Redox couples, and 7.3, Redox disequilibrium, in the GWB Essentials Guide for more info. As for the gold, you should check to ensure whether redox coupling is set up the same way in GSS and SpecE8, and whether you have the same set of constraints in each. Do you have O2(aq) in SpecE8 but not in GSS? Regards, Brian

Hi Sebastian, If there's a problem with your dataset and it can't be read into TEdit or any of the GWB programs, you can still use Notepad or another text editor to view it. When I did this, I noticed an entry "New Mineral" in the minerals section. The blank entry seems to be what's causing your problem. Just remove it from the dataset in Notepad and save your file to fix the problem. I also noticed that a few reactions are duplicated within the thermo dataset. The reactions for U+++ and U++++, for example, appear in both the redox couples and aqueous species sections. And there is an H2(aq) in the redox couples section and an H2(aq)(aq) in the aqueous species section (TEdit tries to add suffixes where species in different parts of the dataset have the same name). I would delete the entries from the aqueous species section so that you have more flexibility over redox chemistry in your models. Hope this helps, Brian

Hi Sebastian, Can you please let me know what GWB release you're using? If you send the thermo dataset to support@gwb.com I'll take a look. Regards, Brian Farrell Aqueous Solutions LLC

Hi Padhi, Rather than setting mineral abundance at each nodal block relative to fluid volume, have you tried setting it as a percentage of the nodal block volume? Assuming your only mineral in the simulation is the general composite that accounts for sorption, you could set its abundance in the initial system (Initial pane) to 61 free volume %. Without setting porosity explicitly on the Medium, the program will calculate 39% for the porosity. Please let me know if that helps. If not, could you attach your X1t script along with your custom thermo and surface datasets? Thanks, Brian Farrell Aqueous Solutions LLC

Hi Johan, Can you please attach example GSS, React, and X1t files so that I can take a look? Please let me know what GWB release you're using as well. Thanks, Brian Farrell Aqueous Solutions LLC

Hi Laner, Sorry for the delay. It turns out the sliding Eh path was originally designed to work when the initial Eh is set explicitly, not indirectly. We've allowed React to swap the electron into the basis before tracing a sliding Eh path if necessary. Please update to maintenance release 10.0.9 for this functionality, or consider upgrading to GWB11. Your script should work if you set Ca++ as the charge balancing ion instead of SO4--, which is much less abundant in your fluid. Regards, Brian

Dear GWB users, We are pleased to announce our latest maintenance releases, GWB 11.0.2 and GWB 10.0.9. The 11.0.2 update allows sliding Eh reaction paths in which the starting Eh is implied instead of specified, fixes a potential crash bug in one of the Gtplot dialogs, fixes an obscure line clipping issue in one of the special plots, and updates graphics in the User’s Guides. The 10.0.9 update allows sliding Eh paths without setting initial Eh, installs a 64-bit code signing certificate, and fixes all known issues. Update your release from 11.0 - 11.0.1 (or 10.0 – 10.0.8, if you have GWB10) at no charge to ensure you have all the newest features and bug fixes. Existing installations should automatically update to this release, unless auto-update is disabled. In that case, users should update their installations from the Support tab of the GWB dashboard. Regards, Brian Farrell Aqueous Solutions LLC

Hi Juan, You need to right-click "Surface species" or any of the listed species (>Ni++, >Pb++ and >Sr+++ in your case) and select "add" to add a new surface reaction to the dataset. Click in the box next to "Species" and choose your As or Zn species. The program will fill in the charge and mole weight of the species from the information in the thermo dataset, but you'll need to supply the Kf and nf. For more information, see sections 9.2.3 (Add and delete entries) and 9.2.5.3 (Kd and Freundlich datasets) in the GWB Essentials Guide. Regards, Brian

Hi, There are various ways that you can set up a model of ARD with the GWB. You’ll probably want to decouple ferric iron from ferrous iron (Config - Redox couples...). In this way, you prescribe a state of redox disequilibrium in your model. When you do this and set up pyrite as a kinetic reactant (add – Kinetic – Mineral… - Pyrite) the mineral will add ferrous iron to solution as it dissolves. You could then set up a kinetic redox transformation (add – Kinetic – Redox) for the ferrous iron oxidation. In fact, you can set parallel rate laws for the iron oxidation. One could be abiotic, while the other could be microbially mediated (add – Kinetic – Microbial reaction). For more information, please see section 7.3, Redox disequilibrium, in the GWB Essentials Guide and section 4, Kinetic Reaction Paths, in the GWB Reaction Modeling Guide. There’s also a useful chapter on Acid drainage in Craig Bethke’s Geochemical and Biogeochemical Reaction Modeling text. Hope this helps, Brian Farrell Aqueous Solutions LLC