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  2. Hello Rob, Thank you for the files. The issue here seems having multiple sample entries with same Sample ID. GSS expects each sample to have a unique Sample ID when entered into the spreadsheet. Perhaps you can add a unique identifier to your samples from different dates in the sample ID? Best regards, Jia Wang
  3. Hi Jia, I've attached my spreadsheet and ternary plot. Thanks for taking a look. Rob Canvasback v1.gss gtplot_CB, ternary, Ca, Cl, SO4.gtc
  4. Hi Rob, Can you attach a screenshot of your Ternary plot and attach the .xtp file so someone can take a closer look? Thanks, Jia Wang
  5. Hi Jia, Yes, I am able to see all 43 samples on the plot, but the legend only shows 14 samples. This is the issue I need help with. Thanks.
  6. Hi Polly, For the two-layer surface complexation dataset, you need to specify a site density or densities for each sorbing mineral. If you don’t, the program can’t account for the existence of the surface. If Ferrihydrite contains both of the sites you defined, >(w1)SOH and >(w2)SOH, your entry might look like this: Ferrihydrite surface area= 600.0000 m2/g 2 sorption sites >(w1)SOH site density= .0050 mol/mol mineral >(w2)SOH site density= .2000 mol/mol mineral You should, of course, supply values appropriate for your sorbing mineral. In GWB14, by the way, you can alternatively specify site density in sites/nm2, as you sometimes see in the literature. You should also remove the entry for >(w) in the surface species section. I’m not sure if it was intentionally put in the dataset like this, or it was a stub of an entry that you didn’t finish, but there’s no reaction, stability, or mole weight and that’s causing a problem. Finally, the surface dataset has a field where the user specifies the thermo dataset to use with it. The aqueous species that are included in the surface reactions, as well as the sorbing minerals, are drawn from the thermo dataset you specify. If you plan to use this surface dataset with your custom thermo dataset, it might be best to specify that custom thermo dataset within the surface dataset. Note that the sorbing mineral you’ve chosen, Ferrihydite, is not in your custom thermo dataset, so you may need to make further modifications to either your thermo or surface dataset. You’ll probably have to make these modifications in a text editor, like Notepad, since TEdit can’t open the unproperly formatted dataset. As for your thermo dataset, I don’t think you should include SiO2, H4SiO4, and Si(OH)4(aq) as separate basis entries. They all represent essentially the same thing. Pick one and write all reactions in terms of that species. Hope this helps, Brian Farrell Aqueous Solutions
  7. Hello Rob, You would select samples to plot in the sample pane of your plot of choice. For example, if you're plotting a Piper diagram, you would double click on the center of diagram once it opens from GSS and select the Samples pane. You can select the samples you want to plot by holding down the 'Crtl' button while clicking. Please refer to section 8 Gtplot in the GWB Essentials Guide for more information. Best regards, Jia Wang
  8. Hello Rob, To select samples to display on your Ternary diagram, double click on the diagram to bring up Parameters for Ternary Diagram dialog. Click on the Samples pane and select samples from the available list. You can press 'Crtl' button while clicking to select multiple samples or click on the 'Select All' button if you want to display all samples. If needed, you can add samples to the "Add" or "Add all" button from the Ignore list to the Available list. Please see section 8 Gtplot in the GWB Essentials User Guide for more information. Best regards, Jia Wang
  9. Hello Kevin, 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 species in your system for Act2 calculation. Perhaps you might also be interested in Phase2 if you are aiming to investigate a more complex set of reactions? Phase2 draws diagrams that may look similar to Act2 in many cases, but the calculation is a complete solution to the equations describing the distribution of mass, just like in SpecE8 and React. You constrain a fluid in terms of concentration, rather than activity and set up reaction pathways, like in React, along the x and y axis. Please visit the Phase2 webpage for information. Best regards, Jia Wang
  10. Hello Anita, Thank you for the additional information. In Ogata 1970, it was stated that the concentration at x = 0 is maintained at concentration C0 through time to arrive at the analytical solution used in your textbook. Please see example 1 and 2 in the paper for details. Furthermore, the problem prompt from your textbook does not state when the leachate stopped leaking into your system. To accurately treat a solute slug problem, like you described above, you would need that information. Therefore, I think you should approach this problem as if the leachate is leaking continuously for the 1-year duration that you are modeling. A couple of other suggestions that might helpful here. You might want to consider extending the length of your domain by a small distance, maybe by 5 or 10 meters. Dispersion is not evaluated at the boundary condition and therefore introduce a bit of error to the node at the boundary. I would suggest you extend your domain length and look at the concentration at the nearest node to 15 meters. It might also be helpful to increase the number of nodes in your domain. With numerical modeling, there's a certain amount of numerical dispersion associated with grid sizes. Increasing the number of nodes would generally help reduce that numerical dispersion. In your case, I doubled the number of nodes to 300 and it helped. However, at the end of the day, model results will differ slightly from your analytical solution due to the estimations made in the numerical method and also consideration of additional variables that the analytical solution might not. For example, the GWB also considers variables like density changes with varying solute concentration which is not considered in the analytical solution. Hope this helps, Jia Wang
  11. I have a ternary plot of 43 samples, but I can't get the legend to show all 43 samples. It only shows 14 samples. How do I get it to show the rest?
  12. Dear Brian, I performed some calculations to obtain the initial chemical composition of pore water in bentonite (MX-80) using GWB code. These calculations have been done by equilibrating the Forsmark groundwater (Table 5.4 in the ppt file) with bentonite with a porosity of 43%, including equilibrium with bentonite accessory minerals as gypsum and quartz (equilibrium with carbonate minerals have also been calculated when considering the MX-80 bentonite), and exchange and surface reactions (Table 5.3 in the ppt file). Table 5-3 and Table 5-4 shows the thermodynamic data used. And according to the above description, enclosed please find the attachments of script, thermo data set and sorbing surface. However, I don’t know why the error message was shown as “bad surface reaction” after running. The other question is how to select SiO2 (aq) or Si(OH)4(aq) in the base pane based on the known concentration of Si in Forsmark groundwater for this case. Thanks for your kind assistance in dealing with my questions. Best regards, Polly Query_about_porewater_chemistry_to_Brian_20200218.pptx SKB pore water calculation.rea thermo_phreeqc_Polly.tdat SOH_Polly.sdat IonEx_Polly.sdat
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  14. When developing pE-pH diagrams for Fe in Act2, when entering the activities for each species, such as the activity for Fe++, am I entering the activity for the ion Fe++ only (as derived from the analysis results from SpecE8 output) or do I need to add up all of the ferrous iron species activities developed in the SpecE8 output and place this total activity in Act2?
  15. Dear Jia ~ Thanks again for your assistance and teaching. The example is from a textbook about mass transport of solutes. You can see the attached file for the original question. Cl- 30mg/L is the value of analytical solution calculated by the formula. I want to get the value of numerical solution by GWB, then confirm the difference between these two method. If I model a continuously leaking point source contamination for 1 year, the wave crest of solute don’t move in the resulting graph (X-position vs. Cl- in fluid (mg/l)) with time and distance. So I think it’s not continuously leaking for 1 year. The time for contaminant leaking should be very short, so we can see the moving of solute slug with time and distance (like figure 11.11 in attached file). Thank you. example.pdf
  16. Hellow~ I tried to build a transport model of carbonate dissolution reaction. However, the following situations were encountered during the simulation: 1.At 60% of the simulation time, the simulation interrupt caused by too large residual error occurs. 2.During the simulation, although the program is still running, the progress will not increase (Xi will not increase, but the reaction simulation is still running). I want to know what caused these problems and how to solve them? Thank you! 白云石溶解(裂缝).x2t 方解石溶解(裂缝).x2t
  17. Hello Anita, If you set up your system to have the contaminant flowing into the domain for an interval period of 1 minute, the concentration of Cl- you will see in the system is going to be much lowered than your expected results. To check, you can set the endpoint of your simulation to 10 minutes (before the simulation fails) and see that the maximum concentration of Cl- by plotting the results. You can plot X-position (on X Axis) vs. Cl- in fluid (mg/l) (on Y Axis) and cycle through the time level in the XY configuration dialog. You will see that the concentration of Cl- in your system is only ever as high as 2.18 mg/l. If you are expecting to see a pulse of contaminant in your domain with the Cl- concentration of 725 mg/l, you will need to have a longer interval where the contaminant is flowing into the system. I tried increasing the contaminant interval to 40 days and was able to arrive at 30 mg/l of Cl- at 15 meters from the leaking point. The error you are seeing are associated with stability issues with in your model. You can try to setting your dx_init, initial time step, to a small value (like 1e-5) to help with stability. To change dx_init, go to 'Config' -> 'Stepping' and you will see an option to set a dx_init value. When I tried using 1e-5 for the initial time step, the model ran to completion but again, I am seeing much lower concentration at 15 m than the answer you expected. Can you perhaps clarify what you mean by instantaneous leaking of the contaminant? And is the 30 mg/l of Cl- an analytical solution? Best regards, Jia Wang
  18. Hi Thomas, I hope you're doing well. I happened to come across this old post and thought you might be interested to know about Phase2, an app introduced with GWB12. The program essentially traces a stacked series of reaction paths, as you'd run in React, to traverse two geochemical variables of interest. You can set up a diagram with sliding log f O2(g) and fixed pH along the y axis, then sliding pH with fixed f O2(g) along the x axis. The basis fluid is defined in terms of total concentrations, as in React, and mass is conserved throughout the calculation. You can also titrate a species into a fluid initially devoid of it to consider a range of total concentrations. By titrating SO4-- in log steps you can make a diagram much like you've envisioned, with the sulfur speciation depending on the y axis variable, log f O2(g). You can render the calculation results in various types of 2D diagrams or in horizontal or vertical cross-sections through the diagram. For the 2D diagrams, you can plot "true predominance" for any basis species or element (the species accounting for the most mass predominates, not the species with the highest activity), mineral assemblage diagrams (which show every stable mineral or combinations of minerals), and render any variable as a color map, mask, or contour. In a log f O2-pH diagram, for example, you can diagram the stable iron minerals under various conditions and contour the concentration of dissolved Fe. Please visit GWB.com/phase2.php to learn more. I'm happy to send a demo if you'd like to try it out. Cheers, Brian Farrell Aqueous Solutions LLC
  19. Hello Twq, I took a quick look at your script and noticed that all your concentrations besides AsO4--- are extremely low. If you are trying to ask the model to charge balance with such low concentration values concentrations, it might lead to stability issues and I think that is the case here. If you want to preserve charge balance, you might want to set a higher background electrolyte concentration, such as 1 or 0.1 molal for Na+. Alternatively, you can also turn off charge balance. To do so, right click on the unit of a basis species and select 'Do not balance'. You might also want to double check your chemical analysis to make sure your initial system concentrations are correct. I see that you swapped in AsO4--- for As(OH)4- and in doing so, the program calculates the species of other As oxidation states base on redox equilibrium. However, you can disable this by deoupling AsO4--- and adding it as a basis species. By decoupling the redox couple, you can constrained AsO4--- independently in your calculations. You might want to try this if you are interested in the speciation of AsO4--- only. Please refer to section 2.4 Redox Equilibrium for more information on decoupling. In the future, you can also check the equilibrium state of your initial fluid before any reaction path takes place by doing a 'Go initial' run ("Run" --> "Go initial"). This is a useful method to check your basis pane setup before adding in complexities of reactants. If the equilibrated fluid from the initial pane looks correct to you, then issues that occur will likely be due to the reactions from the reaction pathway. Hope this helps, Jia Wang
  20. Dear Jia ~ Thanks for your response. In this problem, Cl pollutant is instantaneous leaking to groundwater layer, then compute the Ccl- at d=15m after 1y from the leaking point. Therefore, I set two different fluids in Fluids pane and two reaction interval in Intervals pane. If I set one minute(or one second) reaction interval for the contaminated fluid to enter the system at the inlet and the remaining time flushing the system with dilute fluid, the program cat't run. It shows "residuals too large, 669-th interation, Newton failed at node 0, ............ , Abandoning simulation". What's wrong with this. How can I correct the setting so that the program can run normally? Thank you. 1D nonreact-6instant.x1t
  21. Hello Dirk, I am glad you got your model up and running. It sounds like your convergence issues might be linked to your model running out of minerals. When you run out of mineral(s) or some other reactant in your system, the model will take smaller time steps to try to calculate the numerical solution, which might explain why you received the error “Step is constrained by rate of increase in length of reaction step at node 0”. In this case, you were trying to sorb solutes onto Fe(OH)3 when it is running out, which is probably why your model couldn’t converge. However, I can’t be sure unless I take a look at your input file but that would be my guess. If you would like someone to help take a closer look, please attach your input and thermo file. Hope this helps, Jia Wang
  22. I have a similar problem, please see the attachment. Thanks As_pH=6.rea
  23. Ok, sorted some out. Turns out the contaminated fluid was undersaturated with respect to Fe(OH)3 so by day 8 it has exhausted the Fe(OH)3 and that made convergence not possible for some reason that seems to be related to increase in the length of the reaction step in the first cell. So using goethite instead, seems to be working.... So I am wondering about the why of it. Fe(OH)3 is the adsorbant and is the breakdown because there is no adsorbant left , other minerals (calcite for instance) do go to 0 in the first cell, so does that mean that there has to be some adsorbant left in a cell in order for simulation to go forward?
  24. Hi Polly, Thanks for providing the thermo dataset. I'm taking a look to see if I can offer any suggestions. Regards, Brian
  25. Johan, Some time ago you tried to report the pore volumes displaced from a ChemPlugin instance in GWB12. I’m writing to let you know that GWB14 is now available, and ChemPlugin instances now plot pore volumes displaced and have the value available in the report command. Additionally, React now plots pore volumes displaced from flush and flash models. I hope you enjoy using the software. Cheers, Brian
  26. Sorry posted this on the archive thread... Hi, I am running a simulation of a flow through column experiment and slowly working up to the full rtm. I run the initial solution through for 5 days then the contaminated solution. calcite reacts based on kinetic constraints, precipitation of gypsum, gibbsite, Fe(OH)3 at equilibrium all else suppressed, adsorption using the D&M model and the FeOH database (decreased site densities of w and s sites by an order of magnitude). after adding adsorption I cannot get it to finish. current error is "Step is constrained by rate of increase in length of reaction step at node 0." after 8 days of 10 day run. Any ideas? Dirk
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