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  2. It isn't aphi. I checked and the function is smooth around 239K. It begins to drop steeply at ~ -63C and below -83C it doesn't work anymore. Density function for water looks "normal" at 239K, no rapid changes. May I have look at the database? At the moment I have no idea 😞 Helge
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  4. Hi Jia, Thank you so much. That really helped me out in a big way. Now that I can compute a surface area, I can iterate to see which effective kinetic rate constants best fit my data. Best wishes, and stay safe, Karen
  5. Earlier
  6. Helge, To answer your comments: - I am aware of the martian geochemistry papers (that one and a whole collection of similar papers). This is the reason why I am trying to develop this database. Marion (the paper you cite) uses a code called FREZCHEM which works under 0oC and can model freezing and evaporation. Interestingly I tried to include ice precipitation in the database but this generates an error ("phase rule violation") when running the code but it still shows the saturation index for water ice, which is all you need to see when ice precipitates. - No database is design
  7. Hello Vincent, I am not aware of any thermodynamic database which is able to calculate equilibria down to -80°C. Perhaps it helps to consult https://apps.dtic.mil/dtic/tr/fulltext/u2/a288456.pdf In the context of martian geochemistry some publications are available, e. g. https://www.sciencedirect.com/science/article/abs/pii/S0016703707005844 Another hint: look into Craig Bethkes book about geochemical modeling, chapter on activity coefficients. Water activity is calculated from osmotic coefficient, which in turn is subject of Pitzer coefficients for dissolved salts and of
  8. Hello, I'm trying to run X1t in with some optimization software and it seems to crash when I try using a report command on an simulation that doesn't converge. React gives me "--Error: Run not finished" in a similar situation but X1t just quits. Thanks, Peter
  9. Hello Chelsea, My apologies for the delay. We looked into the issue that's causing Gtplot to crash when plotting XY plots. It seems like there were issue with some internal calculations for conversion units that was causing the plotting program to crash. I identified those by adding calculating the density of your samples using SpecE8 with 1 kg of solution and removed the samples where the density calculation failed. It seems like that helped with the crashing issue. Please find the modified GSS file attached below and let me know if you can launch XY plots successfully. Alternativ
  10. Hello Karen, I believe in order for the authors to set the effective rate constant as the rate_con parameter in this model, they had to choose both the volume fraction and specific surface areas such that the effective rate constant (k) was set to be equal to the intrinsic rate constant (k_+) in equation 8. In other words, the mineral fraction and specific surface area was to chosen so the product of mineral fraction, specific surface area, and the density is one. The volume fraction of 0.01 is chosen since the mineral fraction is not expected to change in the time scale of interest. In t
  11. Hello Vincent, It is hard to say for sure without being able to test your input file along with your thermo database. It sounds like the precipitation of mineral(s) is affecting the activity of water you see and not the other way around. You can test this by turning off precipitation in your model under the Config in the menu bar and choose Options... Uncheck precipitation and run your model again. Do you still see the same jump without any minerals precipitation? If this issue persists, please attach (or email us) your input file and your thermo file so we can look into it further.
  12. I am trying to develop a model for an aquifer I have been studying for years using an approach similar to that descried in Park J., Sanford R. A., and Bethke C. M. (2009) Microbial activity and chemical weathering in the Middendorf aquifer, South Carolina. Chemical Geology 258, 232-241. Specifically, I am at odds as to how the authors set their specific mineral surface areas, which range from 34.9 for dolomite to 36.9 for calcite, as well as what the volume percent of each mineral consider, all of which are listed as 1 volume%. I have attached a portion of this script. Basically, I cannot figu
  13. Hello, I have encountered an issue when running the react code I can't explain. For my research I need to run evaporation simulations well below the freezing point of pure liquid water. Therefore, I designed an extension of the Thermo_phrqpitz database down to -80oC (60, 40, 20, 0, -20, -40, -60 and -80oC). I added numerous minerals and aqueous species along with their pitzer parameters, from recent literature publications. However, when I run the code, I encounter a sudden jump in water activity between 239 and 239.1 K, which I can't explain in any way. This jump affects the water activi
  14. Hello Tuan, Act2 makes calculations for analytical solutions to draw equilibrium lines to show predominant species of the highest activity. Therefore, you should be using the activity of the predominant Fe or Mn species in your system for Act2 calculation. If you don't know the activity of your predominant species and you have a chemical analysis for your fluid, you can run a speciation calculation using SpecE8 to calculate it. You can plot the result from SpecE8 using Gtplot and configure the plot to show species activities. FYI, you can filter on the plot dialog to show you Fe rela
  15. Hello Mukul, I am not familiar with datasets that include NaOCl. If you have existing reactions and equilibrium constant values from literature, you can easily add them into your thermo database using TEdit, the GWB thermo and surface dataset editor, or editing the .tdat as a text file. For more information, please see section 9 Using TEdit in the GWB Essentials User guide or the Appendix for Thermo Datasets in the GWB Reference Guide. Best regards, Jia Wang
  16. Dear ad, When I use Act2 of GWB for creating the Pourbaix diagram for Fe and Mn. I have a question here. For Fe-Mn-H2O system, how the activity of Fe and Mn is calculated before I put the number of this for choosing activity or log activity? If I create the above system, for Fe, I have to choose as Fe++ and Mn as Mn++? Thank you so much for your help, Best regards, Tuan Tran.
  17. Hello Steph, Taking a look at your files, there are a few things that I would suggest you check in your simulations to make sure that you are comparing the same simulations. The default fugacity coefficient model in thermo_hmw.tdat is the Tsonopoulos model. I believe PhreeqC may use the Peng-Robinson model instead. Please check if you are using the same fugacity coefficient model. If not, you can change to use the Peng-Robinson model in React. For more information, please refer to the press_model command in the GWB Command user guide. It seems like you used CO2 fu
  18. I want to investigate reactions when bleach (NaOCl or Ca(OCl)2) reacts with kerogen in black shale (quartz-clay-sulfide). Is there a database that I could use? Thanks.
  19. Hi Jia, Many thanks for your earlier response regarding problems with modelling CO2 solubility in brine. I had actually tried the sliding fugacity method but, while it shows how the dissolved CO2 concentration changes, there seems to be no constraint on how much can be dissolved. I have tried adding as much as 10 molar CO2, all of which dissolves - something which isn't possible! I am attaching files to demonstrate what I have been trying, along with a spreadsheet illustrating the difference between the results I generated with GWB and those I obtained using Phreeqc. I hope t
  20. Hello, I was wondering if someone could help me troubleshoot an issue. I have created a GSS spreadsheet with water quality data for multiple samples and locations to create XY plots, however the Gtplot program keeps crashing when I prompt the request. I am able to create Durov diagrams, piper plots etc, the only type of plot/diagram which keeps crashing is the XY series type. I am sometimes able to convert another type of diagram into a XY series plot, in which case it no longer crashes. I have attached the GSS spreadsheet I used. Note - we inserted a blank sample at the bottom in order t
  21. Hi Sara, I think there are a couple of things to consider when setting up your script. In general, you would need to have two constraints on carbonates to make a calculation for pH. If you don't have that information, you can make assumptions about the constraints on pH, like you have done in your React file, setting the H+ ion in equilibrium with CO2(g) and charge balancing on bicarbonate. However, are you certain that your fluid is in equilibrium with the three sulfate minerals (gypsum, epsomite, and polyhalite) at the same time? You might observe these three minerals in the field but
  22. Hello Anita, I am sorry to hear that you are having issues with activation. Our records is showing that your GWB license is still activated. Were you successful in deactivating your license from your laptop? If not, that would explain the policy fulfill exceeded error. If you still have access to your laptop, can you please double check that the license was deactivated on there and then try activating on your lab computer again? If you still encounter the same issue after deactivating, please let me know. Best regards, Jia Wang
  23. Hello, I activated the geochemist's workbench student edition on my Dell laptop, but had to deactivate it in order to try to use it on the computer in my lab. However, when i tried to deactivate the license on my laptop and reactivate it on my computer in lab, it would not let me. I keep getting activation of the fulfillment is denied by the activation policy because fulfill count exceeded the available seat count [incident#1371-41712]. could you help resolve this issue so i can activate the license key on my computer in lab? Thanks.
  24. Hello all, I’m interested in figuring out how to use GWB to calculate the pH of a water in equilibrium with a simple mineral assemblage and PCO2 at a fixed value. Outside of GWB, one can calculate pH by using 1 or 2 simple assumptions but I’m not sure GWB allows for that. It seems like GWB needs a minimum of two constraints on the carbonate system, such as a designated amount of CO2 and information about carbonate minerals or initial CO2 and an initial pH. However, some of my assemblages do not have carbonate minerals, so I only have information on CO2 and I want GWB to calculate a pH wi
  25. Jia, Thank you for taking a look at this simulation. I did convert to intensive units as suggested (revised input file attached) and got the same result as before as one would expect. However, I still believe the numerical model is failing to correctly simulate the physical system based on multiple lines of evidence: 1) Attached PDF page 1 shows results at 25 and 1000 years. Note the extremely high Ca++ concentration at 1000 years at position 1.5 cm (node 1). More generally I see the Ca species concentrations jumping around in this region for no apparent reason. Physically aqueous Ca
  26. Hello Sylvain, I am sorry to hear about your computer troubles. I have reset your license from our end so you can activate again. Please let me know if you are successful. Best regards, Jia Wang
  27. Hi Jia, Apologies for my late response. I have already determined some of this on my own but I appreciate your solid explanation on the topic. Thank you for replying to my question and including relevant help sections. Sara
  28. Hello, You can calculate the pH of a fluid if you supply SpecE8 with the proper constraints. For example, you can calculate the pH if you know that your fluid is in equilibrium with the atmosphere or a specific mineral. For example, you can swap the H+ ion for CO2 fugacity and charge balance on HCO3-. The program can calculate the pH in a speciation calculation. For more information, please see section 7.2 Equilibrium Models in the GWB Essentials guide. I think you can set up the same method above to set the pH in equilibrium with an aqueous species as well but it would be some
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