Sanjoy

Briliant, Thank you!

Hello there, A colleague of mine collected cation and anion concentrations from local spring waters. Two cations puzzle me: phosphorus and silica. How to I enter them in GWB, as they are not part of the LLNL database? Thank you!

Aha! Thanks Brian, I was indeed looking at the concentration column by mistake. - cheers

Hello, I'm running some water-rock reactions using REACT, and I'm puzzled why the pH that GWB calculates (11.682 in one particular case) is not quite the same as -log( [H+] ), where [H+] in the same case is 2.508e-12, which yields a pH of 11.601. Should I not be paying attention to the sig figs? I was just curious as to how GWB calculates pH, if not by -log( [H+] ) Thanks!

Hello GWB support, I'm investigating the change in fluid pH associated with water-rock reactions with changing water-to-rock ratio (W:R) and temperature. I find that the pH change tracks nicely with the formation of a particular mineral but there is a sudden drop in pH going from W:R = n to W:R = n+1 that I cannot explain. It happens at both high and low temperatures, at the same W:R. I originally thought it was some kind of mineral buffer effect, but I have suppressed everything I could think of to simplify the problem as much as possible following advice from Brian F., but this jump still baffles me. I'd very much value your insight. I'd rather not post my script here, but would be happy to email it to you, as well as xls file with the data plotted. Thanks!

It sure does, many thanks Craig -cheers

Hello, Why is that, when I suppress minerals from the thermodynamic database (using the suppress command), do they still appear under the "mineral saturation states" in the solution (listed in the file obtained by clicking "view results" in the "run" tab)? Thanks!

That indeed helped a lot, thank you!

Hello again, I am investigating carbon speciation in water-rock reactions with changes in temperature. I use React 8.0.10 with thermo.com.v8.r6+.dat as my database. I suppress 32 aqueous species because they don't have data past 25C, so that GWB loads the same amount of species throughout my temperature runs (10C-70C). Yet, CO2 concentrations (mmol/kg) drop by 20 orders of magnitude between 37C and 38C, and I can't figure out what is changing between the runs. All i'm changing is temperature. I'd value any insights! -Cheers case1.txt

Hi Brian, Thanks for the time you spent on this, and for providing a solution. The description of your thought process will be very valuable when I come across this again. - Cheers

Thanks Brian, Sorry for the delay in getting back to you. What you say makes intuitive sense. Because my temperature range of interest is 10C - 150C, the extrapolate option is not entirely wise at this stage, for the reasons you highlighted. What I did do is try to get to the bottom of what causes the unphysical jump based on your response, by suppressing MgH2SiO4, but that didn't do it. I then additionally, and in succession, suppressed NaH3SiO4, CaH2SiO4, Mg(H3SiO4)2, Ca(H3SiO4)2, H4(H2SiO4)4----, H6(H2SiO4)4--, CaH3SiO4+, MgH3SiO4+, but I still get the H2 concentration jump going from 25C to 26C, which baffles me.. Any additional insights? Thanks for your time. wr1.txt

Hello, I'm running a water rock reaction at different temperatures, and I see an unexpectedly high jump in H2 concentration (half an order of magnitude) between running the model at 25C and 26C. That seems very odd, because the concentration, say, between 20C and and 25C is more or less the same, and between 26C and 30C also, so I'm having a hard time explaining the jump between 25C and 26C. I am using the thermo.dat database Attached is the script I load into react (File < Open < Read Script). I was hoping someone could help enlighten me? Thanks! wr1.txt