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From: Sadoon Morad Subject: Two tables for ionic activities in React! When I calculated the ionic activities and mineral saturation indices in react for a water sample I have, I faced two problem for which I have no explanation: (1) I obtained two different tables, in both of which the ionic concentrations are different from my original water composition. It is mentioned for the first table that there are “no minerals in the system� and for the second table some minerals, which were calculated by the software to be in saturation with the water, were used. Which of these tables are correct and relevant to my task (i.e., obtaining free ionic activities and saturation indices)? (2) why are there composite ions in the tables, e.g. NaSO4-, if I am concerned with calculating the free ionic activities and saturation indices? From: Craig Bethke Subject: Re: Two tables for ionic activities in React! The two entries in React_output.txt correspond to the apparent equilibrium state of the supersaturated fluid, and the theoretical equilibrium state of the fluid, once minerals precipitate to saturation. If you don't care to see the second entry, set “precip = off�. To calculate the activity of a free ion (say Na+) from a total analytical concentration (Na), you must determine not only the ion's activity coefficient, but the fraction of the total concentration present as the free ion. In order to do the latter, you must calculate the concentrations of the complex species and subtract these from the total concentration.

From: Paul Foellbach Subject: ANHYDRITE - dataset change I attempt to model the Stability of Anhydrite at 200 bars between 0 and 300 °C.I calculated the log Ks of the reaction ANHYDRITE= Ca++ + SO4— with SUPCRT92 for the Temperatures 0-300 at 200 bars. I replaced the LogKs of the thermo-dataset-reaction of Anhydrite in the data section MINERALS (written with BASIS species) with the SUPCRT-calculated logKs. Here's the script for REACT: Read data for 646 aqueous species, 625 minerals, and 10 gases. > temperature initial = 0, final = 300 > 1 kg free H2O > balance on Ca++ > total molality SO4-- = .028 It is not running. I have to close REACT because of a specific error. From: William F. McKenzie Subject: Re: ANHYDRITE - dataset change Try the following (T initial = 0.01): React> react 500 mg Anhydrite React> temperature initial = .01, final = 300 React> balance on Ca++ React> total molality SO4-- = .028 React> go

From: Paul Foellbach Subject: Cu+ or Cu++-species I attempt to work with the database "thermo_com.R7beta" of Johnson (1998) for GWB. When I include Cu+ to my initial composition of components of the fluid, there appears the message "Cu+ isn't a basis species". In the basis there is only Cu++, so I tried to swap Cu+ for Cu++ in to the basis. Then there appears "Swap species Cu+ is already in the basis", at this point I can't follow anymore. For the "thermo.dat" of GWB 3.0.3 there is Cu+ in basis and I can't swap Cu++ for Cu+, so it's the same problem. Does anyone know how I can work with the Cu+-species or I can solve this problem ? The script of GWB: Initial temperature is 300, final is .01 C Options: Debye-Huckel, flow-through Basis is: H2O .996993972 kg solvent HCO3- total mol = .0024 O2(aq) total mol = -.00409385091 Ca++ total mol = .0190638148 Al+++ total mol = 2.51351966e-6 Mn++ total mol = .00047395402 H+ total mol = .00834655421 Cl- total mol = .580875652 Na+ total mol = .517296407 Mg++ total mol = 6.60314937e-6 Fe++ total mol = .00224268778 SO4-- total mol = .0040159751 K+ total mol = .0192577736 SiO2(aq) total mol = .00762498287 Zn++ total mol = .000993259417 Cu+ total mol = .000838616032 React> go Solving for initial system. -- Entry Cu+ is not a basis species or a decoupled redox species. (Type "show basis" or "show couples" for more info.) React> show basis Basis species in thermo dataset: H2O HCO3- Ra++ Ag+ HPO4-- Rb+ Al+++ He(aq) ReO4- Am+++ Hf++++ Rh+++ Ar(aq) Hg++ Rn(aq) Au+ Ho+++ RuO4-- B(OH)3(aq) I- SO4-- Ba++ In+++ SbO2- Be++ K+ Sc+++ Bi+++ Kr(aq) SeO3-- Br- La+++ SiO2(aq) Ca++ Li+ Sm+++ Cd++ Lu+++ Sn++ Ce+++ Mg++ Sr++ Cl- Mn++ Tb+++ Co++ MoO4-- TcO4- CrO4-- NH3(aq) Th++++ Cs+ Na+ Ti(OH)4(aq) Cu++ NbO3- Tl+ Dy+++ Nd+++ Tm+++ Er+++ Ne(aq) UO2++ Eu+++ Ni++ VO2+ F- Np++++ WO4-- Fe++ Pb++ Xe(aq) Fr+ Pd++ Y+++ Ga+++ Pm+++ Yb+++ Gd+++ Pr+++ Zn++ H+ Pt++ ZrO++ H2AsO4- Pu++++ O2(aq) React> swap Cu+ for Cu++ -- Swap species Cu+ is already in the basis From: Tom Meuzelaar Subject: RE: Cu+ or Cu++-species For both datasets Cu+ and Cu++ form a redox couple. If you decouple them, you should be able to work with the two species independently.

From: Ross McCartney Subject: Ion exchange calculations I have been looking at the ion exchange example that came with GWB. Does anyone know whether the ion exchange function works at temperatures other than 25oC? If so, how do I implement this? When I change the temperature, I only get sorbed data for Na. From: Craig Bethke Subject: Re: Ion exchange calculations By default, the ion exchange model operates at 25°C. To apply it at other temperatures, set “extrap = on�.

From: Wang Lian Subject: adding sorption sites I am trying to add some surface sites (for sorption) other than iron oxides into dataset HFO+.dat, e.g., Gibbsite as a sorbing surface. I can't seem to do that as I got error message as: React stop: set_bascomp: lost element -- Hit any key to quit React. From: Craig Bethke- Subject: Re: adding sorption sites The solution to this problem is easy: you need to have a separate dataset for each type of surface you want to consider in your simulation. The reason is that React figures the surface area for each surface type separately, by summing over the minerals with that surface type. So split the dataset into two files, one for ferric iron, the other for alumina. Then open both in your React session, and you're done.

From: Nick Tosca Subject: reacting basaltic glass I am currently running experiments involving basaltic glass dissolution and am wondering what the best way is to express a glass in GWB to equilibrate with a variety of solutions. From: Craig Bethke Subject: Re: reacting basaltic glass There are two ways to simulate the reaction of basalt with aqueous solutions. First, you can set as reactants the minerals that make up the basalt, and titrate them into the fluid. Or you can set oxides as reactants. The first method is useful when you wish to account for dissolution at rates that vary among the minerals -- i.e., non-congruent dissolution of the rock. The second can be convenient since it allows you to use a bulk analysis directly, and to account for any glass fraction implicitly.

From: Enrique Portugal Mari­n Subject: ph-Calculation I am just starting to use gwb to applied to geochemical modeling to be used in geohtermometry of hot spring developed in igneous rocks. I followed the example in Bethke's book, but instead swap CO2 for HCO3- I used HCO3- data. I noticed that gwb pH calculation is based on CO2 to give bicarbonate and H+. Can gwb make a pH calculation more rigorously that involve pH-dependent ions like SiO2 (H2SiO4), NH4+ etc ? From: Craig Bethke Subject: Re: ph-Calculation Yes, you can use any pair of species that form a protonation reaction to constrain pH. Just add or swap each into the basis, and then for each constrain concentration, activity, or fugacity.

From: Andy Wilde Subject: Species with O2(aq) I am attempting to simulate the interaction between an hypothetical ore-forming brine and a shale-like host-rock at 200 degC. My question concerns the plotting of species with O2(aq). As the attached plot shows (*.cgm) a number of species are plotted that do not contain O2(aq). Can anyone explain why this is? From: Craig Bethke Subject: Re: Species with O2(aq) The species in your plot do indeed contain O2, but in negative amounts. For example, H2S(aq) = SO4-- + 2 H+ - 2 O2(aq). There is a discussion in the green book on the choice of components and why components can be present at negative mass.

From: Richard Laffers Subject: pH buffering I encountered two problems while using GWB: 1. REACT: I wonder how can I buffer pH by a certain reaction during reaction path. For instance, I wish to model cooling of hydrothermal fluid from 300C to 200C while pH in the system is buffered by the reaction Annite + .5 H2O + 3 H+ + 3 Albite = 7.5 Quartz + Maximum_Microcline + 1.5 Chamosite-7A + 3 Na+ e.g. annite to chlorite conversion, at the presence of Qtz, Alb, Microcline (=other rock-forming minerals present in my system). (I got this reaction running the script annite2chamosite.rxn). Since pH of the reaction is temperature dependent, simple fixing pH on the Reactants pane is not reasonable. Sliding pH would have been applicable only if pH was linearly dependent on temperature. Is there currently a way to buffer pH by a reaction in the React program? 2. ACT2, TACT: I wish to draw Eh-pH and T-pH diagrams concerning stability and coexisting of Annite and Chamosite (or Annite and Daphnite). Running any of the attached scripts did not yield satisfactory results, as I couldn't force both phases to be present at the diagram. Does anybody know how to deal with this? { WinXP Proffesional + SP1, GWB 4.0.3, thermo.com.v8.r6+.dat } +++ annite2chamosite.rxn +++ # Rxn script, saved Mon Feb 09 2004 by ja data = "C:Program FilesGwbGtdatathermo.com.v8.r6+.dat" verify temperature = 300 C react Annite swap Quartz for SiO2(aq) swap Maximum_Microcline for K+ swap Albite for Al+++ swap Chamosite-7A for Fe++ log activity H2O = 0 pH = ? log activity Na+ = 0 long +++ diagram_BT-CHL.ac2 +++ # Act2 script, saved Mon Feb 09 2004 by ja data = "C:Program FilesGwbGtdatathermo.com.v8.r6+.dat" verify temperature = 300 C swap Annite for Fe++ swap e- for O2(aq) swap Quartz for SiO2(aq) swap Maximum_Microcline for K+ diagram Annite on Eh vs pH log activity main = 0 x-axis from 0 to 14 increment 1 y-axis from -1.5 to 1.25 increment .25 +++ diagram_BT-CHL_Eh.tac +++ data = "c:program filesgwbgtdatathermo.dat" verify swap Annite for Fe++ swap Quartz for SiO2(aq) swap Chamosite-7A for Al+++ swap "Maximum Microcline" for K+ swap e- for O2(aq) diagram Annite vs pH log activity main = 0 Eh = -.1 x-axis from 0 to 14 increment 1 y-axis from 0 to 300 increment 10 +++ diagram_BT-CHL.tac +++ data = "c:program filesgwbgtdatathermo.dat" verify swap Annite for Fe++ swap Quartz for SiO2(aq) swap Chamosite-7A for Al+++ swap "Maximum Microcline" for K+ diagram Annite vs pH log activity main = 0 x-axis from 0 to 14 increment 1 y-axis from 0 to 300 increment 10 +++ diagram_BT-CHL+Al.ac2 +++ data = "C:Program FilesGwbGtdatathermo.com.v8.r6+.dat" verify temperature = 300 C swap Annite for Fe++ swap e- for O2(aq) swap Quartz for SiO2(aq) swap Maximum_Microcline for K+ swap Chamosite-7A for Al+++ diagram Annite on Eh vs pH activity main = 1 x-axis from 0 to 14 increment 1 y-axis from -1.5 to 1.25 increment .25 From: Craig Bethke Subject: Re: pH buffering (1) To buffer a system in React by equilibrium with an assemblage of minerals, simply swap the minerals into the basis. If the assemblage is not stable (which is probably trying to tell you something), you can maintain the mineral assemblage by turning of the "precip" option, or by suppressing the mineral(s) that become supersaturated. BTW, the mineral assemblage you cite buffers the Na+/H+ activity ratio, not pH. (2) You don't see minerals Chamosite or Daphnite in your Act2 results because they can't be made up from the basis entries you specify, and hence aren't part of the chemical system. You can see the species considered in constructing a diagram by clicking on the "Log" pane, or by inspecting the output file (Run -> View -> Act2_output.txt). To get the diagram you describe, try swapping Microcline for Al+++, then setting a K+ activity.

From: J.L. Fernandez-Turiel Subject: Meaning of ppd What means (ppd) after Fe(OH)3? From: Craig Bethke Subject: Re: Meaning of ppd Jose, I've always assumed it meant "precipitated". From: Criscenti, Louise J Subject: Re: Meaning of ppd I've always thought that too - but I think it also implies amorphous or nanocrystalline (hydrous ferric oxide). From: Mark Logsdon Subject: Re: Meaning of ppd My understanding is that it refers to a specific set of data (traceable through the reference string) for "HFO" precipitates for which the underlying thermo data were derived. It probably is the case that the physical materials that are traceable to source were, as Louise states, X-ray amorphous or nanocrystalline, but could also have included some mixture of different states or even compositions.

From: Braden Subject: Batch Process Crashing I am currently working on a project where I am using react to speciate numerous water samples. I have written a react script that inputs the data, runs react, and renames the react_output.txt files so they are not overwritten. My PROBLEM is that when react has processed 508 files, it crashes. This happens for any batch file I have made with more than 508 separate runs. The error messages state "could not open react_plot.gtp file. (do you have permission to write in this directory?)", "Could not open react_output.txt.(do you have permission to write in this directory?)", and then "can't find file C:program filesgwbgtdatathermodata.dat. ok to list files?". This file is "not found" even when you browse to it and select it from the list. Then when you select quit (since you can't select a thermo data file, the resume_react files are not found and the application (Gwb) crashes with an application error. Any ideas?

From: Nikolay Sidenko Subject: Fe(III) in AMD Please could you help me with modeling acid-mine drainage solutions? I would like to create diagram pH-[so4] diagram in Act2 in presence of Fe(III) and K. I'm a new user and my particular question is about input of Fe(III) activities. I do have two options. The first option is input measured molar concentration of Fe(III), which was analytically measured. Usually when people build such diagrams they refer to concentration of total Fe (III)in the solution. I assume they use it as input for calculations. Second is run a program like WATEQ4F, MINTEQ .. inputting analyzed Fe(III) and other components of the solution to calculate activity of Fe(III) taking into account formation of complexes, FeSO4-(aq) for example. Molar concentration (the first option) is 2-3 orders of magnitude higher than speciated one (second option). Diagrams for those inputs look quite different. Which way should I use? I will appreciate any advises or references. From: Mark Logsdon Subject: Re: Fe(III) in AMD Dear Users, a week or so ago, I responded directly to a request from a new user for some information on approaches to using the GWB models to evaluate some issues in the chemistry of Fe in acid-mine drainage. Some of the matters that arose during our conversation may be of somewhat more general interest, particularly to folks who are new to GWB. In hopes that this may be true, I forward some of the discussion. If you think I'm nuts or have questions, give me a shout. ----- Original Message ----- Let me have a quick go at your questions in the same order you ask them. 1. Activities. I take it that when you say "... precipitating from my AMD samples" you have actual waters that you are studying (or perhaps have generated experimentally.) Maybe I am too plodding a geochemist, but I always begin my analysis by running a simple speciation model. You do this in GWB (REACT) by inputting your water analysis and saying "go" (or using the run function from the menu). Actually, before that even I usually do a charge-balance check on my analysis, which I do in an EXCEL spreadsheet that I produced using factors from Hem (1985). If there is an issue, I want to know it before I invoke the real model, and this also allows me to look at my analysis one more time, perhaps to help decide how I want REACT to set the charge balance (e.g., using Cl, SO4 or something else). My prejudice for AMD solutions is that the parameter most likely to be imprecise is SO4, so I usually change the REACT default from Cl to SO4. Of course, you have to be convinced that the problem is on the anion side - if the analysis does not include Al, Fe, Mn and probably some other metals, too (Cu, Zn - depends on the source ore, of course), then the charge balance problem may lie on the cation side, in which case you may have to go back to your ICP data and sort through the metals again. But assuming I have a good match, then I pop the analysis into REACT, and start to work with it. As you know from reading the documentation, REACT is a path-seeking code, using a minimization-of-free-energy routine to do its equilibrium calculations. So, if you just put in your analysis and leave REACT on the default settings, it will give you two sets of outputs. The first, called step 0, is the standard distribution of species calculation for the input chemistry, including activities (and activity coefficients). It also will print out the Saturation Indices for a whole bunch of minerals,but in this step it does not change any solution chemistry. Then it prints out "Step 1", which does the *default* equilibrium calculation for the water you input. For your waters, for Fe it almost surely will go directly to Hematite, because for the LLNL database that is the ferric oxide with the lowest Gibbs Free Energy. Of course, this will hugely deplete the "equilibrium" solution in Fe, and all the other Fe phases will be "undersaturated" (i.e., negative SI). But you know that Hematite will not precipitate directly from your AMD water at say 10 C (or whatever your field T is), so this automatic step is not very useful. Two choices at the preliminary phase. Keep everything in default mode and just pay no attention to the "Step 1"calculations. Or, before you run the distribution, input "precip off". This will then limit the output to the initial distribution of species. Long story short: You can get the activities in GWB, using REACT. There are some advantages to this compared to using WATEQF extrenally as a prior step, most importantly, the thermodynamic databases in GWB are internally consistent from module to module. The database for WATEQF is not entirely compatible with the LLNL database. 2. If you think that all the Fe in your solution is Fe3+, then you can just swap Fe3+ for Fe2+ and enter your value. If you have both, then you need to decouple and control the concentrations of each separately. 3. By "checking the output", I just meant that you can have ACT 2 print out the equations and work through them to be sure that the figure in generates makes sense to you. This is okay as an exercise for students, but I usually count on the University of Illinois programmers as getting the arithmetic right and just work with the figure. [This may or may not be "good for the soul", but what it certainly limits the systems most of us had the strength to analyze.] 4. There is nothing in ACT 2 that prevents you from entering your entire water chemistry, and in fact, I suggest that you do - or at least as much of it as makes any difference to the phases you are concerned with. For example, if you have very much Mg in your real water, then it will be extremely important to the speciation of SO4, and if you don't account for it, you will have too much SO4 "available" for your secondary phases, predicting greater stability than they actually would have. If you have both Fe2+ and Fe3+, then I strongly urge you to include both in your input file. One last thing that you didn't ask about, but will need to address. The default thermo database for GWB does *not* include schwertmannite. You can check the alternative database to see if it is there. If it is not in the GWB databases, then you need to modify the database you want to use to add it. Read the User Guide CAREFULLY about how to do this - always copy the database, then use the copied version for modifications. Obviously, you are going to have a hard time modeling relationships of jarosite and schwertmannite if one of them is not in the database. Modifying the database in GWB is pretty straight forward, assuming you have the basic data to work with

From: Larry Hull Subject: Problems with version 4.0.3 I run GWB on a 2 Ghz Dell PC with Windows XP Professional GWB version 4.0.3 I am having two intermittent problems with GWB. 1) In previous versions, the command - line interface was always very quick. In this version, the command line prompt sometimes goes to sleep after a couple of input lines. The program continues to run and I can use the GUI to enter data. However, if I use the command line interface, after I hit enter, nothing happens. Anybody else having trouble with the command line interface being very slow or stopping while the GUI interface continues to work? 2) When drawing diagrams in act, I can draw one diagram, but if I attempt to draw a second diagram with slightly altered parameters, I sometimes get the message "Water is not stable in this region" however, if I go back to the system just drawn, I get the same message "water is not stable". (and the systems I am drawing are in the water stability region). If I do the second drawing first, it works indicating that the message was not right in the first place. I have completely uninstalled GWB and reinstalled from scratch. That was not help at all. From: Craig Bethke Subject: Re: Problems with version 4.0.3 We have not seen or heard of either of these problems, but want to make sure that it is not our software at fault. W/r to (1), in which of the GWB programs does it occur? Is there any pattern (specific commands typed in the command pane, for example) that seems to trigger the behavior? The next time it happens, please email us your history list: go to C:Documents and Settings<username>Application DataGWB and send us the appropriate file (e.g., react_history.dat). W/r to (2), can you send us a script that demonstrates the issue? Again, next time you see the behavior, send us your history file. Unfortunately, intermittent problems can be difficult to track down. The majority of cases in which multiple unusual problems are reported turn out to be software conflicts, hardware issues, or viruses on the user's computer, but we will try to locate any faults in the GWB apps that might explain what you see.

From: KV Ragnarsdottir Subject: Macs and PC simulation Can you please tell me whether anyone has been successful in using Workbench on a Mac with a PC simulator. If yes, which Mac operating system and which PC simulator have you used. From: Alexander Smirnov Subject: Re: Macs and PC simulation Unfortunately, I am not a Mac user, but on a "not-so-unrelated" note I have been successfully using GWB (3.x and 4.x) on Linux (Red Hat 9.0 and SuSE 9.0) using a virtual Windows simulator (VMware 3.x, 4.x). Other choices to run GWB from Linux include "Wine" or SuSE's "Wine Rack". Also - you can find some answers on the GWB users' website (http://gwb.geo.stonybrook.edu). Just search the site for "Mac" and the first two hits will directly address your problem. From: Daniel Layton-Matthews UTD Subject: Re: Macs and PC simulation I use GWB on a Mac using OS X, but I use the Remote Desktop Connection (RDC) that is free to download from Microsoft. The problem with using Virtual PC with GWB is the HASP (dongle) does not communicate with Virtual PC (or at least I couldn't get it to work). The software installs perfectly on Virtual PC, but it will not run the HASP license software. As with any program in Virtual PC, it runs very slow. So, I switched to RDC. You need to have access to a PC box that is running XP pro or Windows NT server and has GWB installed with the dongle. By using RDC, Windows appears in a terminal window and you run GWB as if you were at the PC box. Most Macs have dual monitor support by default and you can setup RDC to use the second monitor. GWB runs as quick as the PC box will allow. In fact, it is much quicker than the any version of Virtual PC that I have used. At times I have three operating systems running at the same time without any problem (OS X, XP and OS 9). People might ask "why not use the PC box itself?". By using RDC I can store any data or scripts that I use directly on my Mac, which is handy for plotting and writing. Also, RDC works from other PC's, so you can have one dedicated machine for GWB, but anyone with a user account on the XP machine can use the program, albeit one at a time. For those labs that have a tight budget and cannot afford the multi-user license, this is a nice alternative. RDC also works for any PC program. We have our Elan 6100 ICP-DRC-MS running XP and I can operate it via RDC from my office or from home. I can watch sample progress and even shut the machine down. From: Don L. Shettel Subject: Re: Macs and PC simulation For several years I ran GWB 3.x on a Mac PowerBook G3, 500mHz, Mac OS 8.6 through 9.2, with Virtual PC 5.x. Instead of the dongle, you need to obtain the software Flex-M license. It may be a bit slower than running directly on a PC, but it still seemed fairly fast for what I was doing. I am currently working on upgrading to virtual PC 6.1, GWB 4.1, and the PowerBook is already running Mac OS X. The reason for some problems here is that I swapped out the PowerBook internal HD for a larger one, and put the old internal HD in an external enclosure. The Flex-M license is tied to the hard drive, and perhaps computer as well, which may be causing me some problems. However, in your case, with a fresh software license on a Mac OS X computer, and a fresh version of Virtual PC 6.x, you should have no problems. I am not implying that software upgrades cause problems, but changes in hardware configuration might with the Flex-M license.

From: Robert A. Zierenberg Subject: Emulating GWB on MAC I recognize the GWB does not support Macs, but I understand there are folks out there running GWB using Virtual PC. I have tried to load GWB on my G4-Ti laptop using OS 9.2 and versions 5.0 and 6.0 of Virtual PC. The program appears to load in the emulated Windows 2000 PC, but no files appear. Comparing this installation to that on a real PC shows that after the installation module that deals with the HASP runs, the confirmation and dialog boxes that we see on a real PC don't show up on the Virtual PC, so I expect the problem is lies in this part of the installation. I would greatly appreciate any advice on how to proceed with installing GWB on a Mac (and any other advice about pitfalls of using Virtual PC to run GWB from those who have attempted this route). I apologize for sending this to the list if the answers are in the archived messages, but I was unable to access that site.

From: James Cleverley Subject: osmotic coefficients (again) I am having trouble locating the exact reference source for the equation used to calculate the osmotic coefficient for NaCl salt solutions and used in GWB to calculate water activity. The equations and some regression coefficients are reproduced in Bethke (1996) as eq. 7.8, 7.9 and the table on page 114, however where in the literature are these defined and reproduced? The reason I ask is that I am having trouble reproducing the graph in Figure 7.5 of Bethke (1996) using the data on page 114 and equation 7.8, 7.9 and 7.7 (plus the A parameter from the GWB datafile) I am calculating much lower water activities at high Is. Any pointers to the original source of the regression data and those equations would be really appreciated. From: Craig Bethke Subject: Re: osmotic coefficients (again) Bill Bourcier and Tom Wolery provide the following information: The oiginal literature reference is Helgeson, Brown, Nigrini, and Jones (1970) GCA 34:569. The actual parameters in the regression were taken from the PATH code, developed in the 1960s; it may (or may not) take some digging in the literature to find precisely how the parameter values were derived.

From: Kevin Telmer Subject: predicting mineral precipitation in porewaters I would like to enter multiple transition metals and trace-elements and SO4-, Eh, and pH into GWB, and have it work out which metal sulphide will precipitate first due to decreasing Eh at various pH's. Is this possible with Act2? My only progress so far are mosaic diagrams but they really just overlay two diagrams and so leave out many other possibilities. From: Craig Bethke Subject: Re: predicting mineral precipitation in porewaters Probably to best way to do what you describe is to trace a sliding Eh path with React, and then use Gtplot to diagram the results.

From: Susan Brantley Subject: saving and exporting graphs How do you save or export graphs from GWB and from XT1 and XT2? From: Craig Bethke Subject: Re: saving and exporting graphs (1) Click on File -> Save Image... and save the plot in your choice of graphics formats. (2) Copy to the clipboard and paste into your document.

From: Wang Lian Subject: Effect of confining pressure on stability of minerals To study pore water chemistry, we use high pressure (30 Mpa) squeezing technique to extract pore water from clay cores. The pH of the squeezed water was found lower than expected. Trying to interpret the observation, we are looking at two things: effect of the pressure on the double layer and on the stability of minerals. The clay we are studying contains few percents of pyrite and calcite, of which the stability/solubility may have impact on pH. We are trying to treat the pressure using thermodynamics but wandering what mechanisms to consider. Craig, in your FAQ list of GWB, the effect of pressure is not a big issue with exceptions such as sulfate minerals. Can you direct me to some relevant literatures about pressure effect? Any other suggestions are welcome as well. From: Lauren Browning Subject: Re: Effect of confining pressure on stability of minerals I know of a situation that may be somewhat analogous to yours. Yang et al used high pressure (e.g. hundreds of MPa) uniaxial compression to squeeze pore waters out of volcanic tuff at Yucca Mt., NV. Bill Murphy and I evaluated the measured pore water compositions, and found some thermodynamic inconsistencies between the measured pH and the reported concentrations of various C-bearing species, among other problems. John Apps also looked at the data, and found additional types of problems. Both groups used correction methods to reinterpret the measured water compositions. I don't know if these reports would be of any use to you or not, but I've copied some of the references below. Yang, I. C., Rattray, G. W., and Yu, P., 1996. Interpretation of chemical and isotopic data from boreholes in the unsaturated zone at Yucca Mountain, Nevada. U.S. Geological Survey, WRIR 96-4058, Denver, Colorado. Yang, I. C., Yu, P., Rattray, G. W., Ferarese, J. S., and Ryan, R. N., 1998. Hydrochemical investigations in characterizing the unsaturated zone at Yucca Mountain, Nevada. U. S. Geological Survey, WRIR 98-4132, Denver, Colorado. J. A. Apps LBNL-40376, UC-814, 1997 Browning L., et al. (2000) Thermodynamic Interpretations of Chemical Analyses of Unsaturated Zone Water from Yucca Mountain, Nevada. Nuclear Waste Management Symposium Proceedings. Materials Research Society.

From: Andy Wilde Subject: wt% oxide I am trying to simulate an interaction of a hot brine with a pelitic meta-sediment. The software is React 4.0.1 The plot shows the wt% of elements in the rock with increasing fluid throughput. As you can see the totals far exceed 100%. From: Craig Bethke Subject: Re: wt% oxide When in Gtplot you choose concentration units (ug/kg, mg/kg, g/kg, wt%), you are plotting mass of something per unit mass of aqueous solution. This holds whether the “something� is dissolved, sorbed, or precipitated. So looking at this plot, you might reasonably expect wt% to represent mass fraction in the rock (since you cannot see that the pulldown list from which the creator chose the unit for the y axis), it is simply a plot in concentration units.

From: Anne Taunton Subject: Reaction trace plotting problems I am having trouble plotting a correct reaction trace on an activity-activity diagram in GWB release 4.0. I have attached my input files along with a .cgm file of what is plotting on my activity-actvity diagram. The React output has talc, tremolite and chrysotile saturated by the end of the reaction. However, when I plot the reaction trace, it plots only in the chrysotile stability field. I have made sure that the working directory and React_plot file are correct. A friend of mine has plotted the reaction trace in a previous version of GWB, and it plots correctly in his version. Has anyone else had this problem with version 4.0, or am I missing something? Attached files: Win, Mac: [general_q53.rar]; Linux: [general_q53.tar.gz] From: Craig Bethke Subject: Re: Reaction trace plotting problems Yikes, that certainly is wrong. The problem is fortunately confined to Act2, when you project traces onto diagrams which use activity ratios on both axes. We will fix this and include the correction in a patch that we will distribute soon.

From: Robert Pelton Subject: Calcium carbonate with adsorbed polymer I would like to model calcium equilibria in the presence of polyelectrolyte solution. Has anyone done this?

From: Paul Foellbach Subject: pH and/or CO2(aq) ? I like to model a composition of a fluid which is characterized by earth- and alkali elements, metals, H2S(aq), Alkalinity and, pH and CO2(aq). CO2(aq) has to be swapped for H2O, H+, HCO3- of the basis. HCO3- is set by the Alkalinity, and H2O builds the main part of fluid, H+ is set by the pH. So can I state the concentration of CO2(aq) and pH of that fluid ?

From: Paul Foellbach Subject: decoupling HS- I attempt to model the mixing between seawater and brine. I would like to realize a Equilibrium and Disequilibrium model. Equilibrium of HS-: If I model the Sulfate-Sulfid-Equilibrium (all couples of database are coupled), the resulting dominant aqueous S-Species is H2S(aq) (ca. 2 mmolal). Disequilibrium of HS-: If I decouple HS- to inhibit the sulfate-sulfide equilibrium, HSO4 is the dominant (ca. 2 mmolal) aqueous S-species. The resulting S-Metal-minerals from equilibrium calculation are Sulfides. The resulting S-Metal-minerals from disequilibrium calculation are Oxides and no sulfides. I can't understand the dependance of S-speciation on Dis- or Equilibrium conditions ? The initial S in solution is speciated as H2S(aq). Why does the speciation of S in solution depend on equilibrium or disequilibrium at the first calculation (Equilibrium or Diseqilibrium) step. In my opinion the INITIAL (first step of equilibrium calculation) concentration of H2S(aq) = 2 mmolal in a solution doesn't change neither at equilibrium nor at disequilibrium calculation of HS- and SO4-speciation, because at the first step H2S(aq) is concentrated at 2 mmolal and not 2 mmolal HSO4. I would appreciate any help to understand these points.

From: Joel Brugger Subject: Pressure - and general comments Correct me if I am wrong, but I understand that GWB can only work under vapour saturated pressures, up to 300 C. There is really no theoretical reason for this limitation - only historical ones. We have ways to estimate properties over a wide range of temperatures and pressures. I suggest that the inclusion of the SupCrt database and algorithms into GWB would be a very valuable addition to the program!!! From: Craig Bethke Subject: Re: Pressure - and general comments The GWB can work at any pressure, and pressure can vary with temperature. The pressure curve is set within the thermo database, in a table near the top. As you note, geochemists generally compile thermo data at 1 atm (below 100 C) or along the steam saturation curve (100 C and above), because these are the conditions at which the data is collected. Furthermore, there's little impetus for compiling data at other pressures because the change in log K with pressure for most reactions is commonly considered small compared to the uncertainty in this value (there are notable exceptions). But you can create a database for any pressure conditions by correcting the stability constants for species and minerals (according to the well-known formula involving the standard volume change of reaction) in the dataset, and then setting the pressure table at the top of the file. You can use a program like SUPCRT to do this, but it's a simple calculation to do by hand or with a spreadsheet. I might note that when people inquire about the effects of "pressure", they are almost invariably referring to the partial pressure of a gas such as P-CO2. Such variables of course can have dramatic effects on solution chemistry. In the GWB, you set partial pressure (actually fugacity) directly with the "fugacity" command; the discussion above applies only to the more subtle effects of confining pressure on mineral and species stability.