Karen Johannesson

Hi Jia, Wow. I would have never caught that extra space. I have made a number of databases in the past and never had an issue. I reckon I never added a space there before. I also eliminated the tabs and changed them all to spaces. I'll give the model a run and see what happens. I hope this works. Assuming it does, then the next step will be "tuning" the kinetic mineral rate constants to fit our data as best as possible. Thanks. Karen

I also sent these to support@gwb.com

Let me try. First is the database. And second is the script. Note that I haven't included the dll file. Although I compiled one, it the script does even get that far. thermo_ionx.tdat Carrizo_Weathering_5.x1t

Dear Jia, I haven't yet tried to use your suggestion because I am perplexed that when I try to run my script, X1t does not seem to recognize either of the pseudo minerals that Park et al. (2009) provide the recipe for adding to the thermo.tdat dataset. I have been able to get the compiling worked out by downloading the compiler for VS 2019. Also, when I try to run my script, the proper database is loaded "thermo_ionx.tdat", which is the thermo.tdat modified by inclusion of the pseudo minerals Na2EX2 and CaEX2 as per Park et al. If I open up the X1t module, and load thermo_ionx.tdat, and add Ca++ or Na+ to the basis, I can swap them for the pseudo minerals CaEX2 and Na2EX2, respectively. But when I try to run my script with kinetic Na2EX2 or CaEX2, I get an error that says "Could not identify reactant species Na2EX2" (see attached). I have attached another script I used in a previous paper where I made up a pseudo mineral that I called Arsenogoethite that runs fine. I am perplexed. I don't know why this is not reading Na2EX2 or CaEX2. Any suggestions would be greatly appreciated. Best wishes, Karen

Hi Jia, I have made pseudo minerals before (e.g., "arsenogoethite" in a paper I published in GCA at the end of 2019), so I was perplexed by the modified thermo.tdat database not seeing it when I tried to run X1t. I like to work from scripts and less so from the GUI, but maybe I'll try this approach you outline above. I wasn't making a surface dataset, because I was following the approach of Park et al. (2009) to add the pseudo minerals Na2EX2 and CaEX2 directly to the thermo.tdat file. I need to be able to "turn on" the cation exchange reaction for only a portion of the flow path because it appears to only begin to become important after about 26 km of flow. This is also why I was following the script of Park et al. Eventually, when I have the model running and doing a good job of simulating the major ion chemistry along the flow path, my final addition to the model will be for simulating the fate and transport along the flow path of a set of trace elements. I have already built the FeOH_trace element.sdat surface database for that. I have done this (make SCM surface databases) before for arsenic species, tungsten, organic matter, and so forth. At the moment I am trying to compile C++ dll files, but haven't had any luck. I used to be able to do these things without any problem when I was just using a clunky old Dell PC clone. Something about using Parallels and compiling C++ codes is truly perplexing to me. I should be able to do this as all my other PC compatible software, including GWB, runs fine on my Mac using Parallels. If I can solve this issue, then I am hoping my question above will be answered once and for all. I had a similar issue when I was running microbial respiration for Fe(III) oxides with GWB. I could compile the C++ code on my Dell, but could never get it to work in my Mac using Parallels. Thanks, Karen

I thought I had posted this question yesterday, but it seems to be lost. Anyway, I have been trying to model cation exchange in X1t without having to build a dll library in C++. Instead, I was wondering if this could be done with a simple basic script. Again, I am following the approach of Park et al. (2009), and have added the "pseudo-minerals" Na2EX2 and CaEX2 to the thermo-tdat data base. I also wrote basic scripts (example for Na2EX2 rate law) to see if X1t will evaluate them. However, I can't seem to coax X1t to recognize the "pseudo-minerals". Do I absolutely need to instead write a C++ code and compile it as per Park et al (2009) to get this to work? Na2EX2_Rate.bas.pdf Kinetic Ion Exchange.pdf Park et al._script.pdf

I have written custom rate law scripts in BASIC describing mineral dissolution precipitation that I have used successfully with React (see attached example for anorthite). Can I do the same thing with X1t? I would like to write similar scripts for cation-exchange along a groundwater flow path.

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

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 figure out how these numbers were generated. My best guess is that the authors chose values for the effective rate constants (which are what the rate_con values are in the script and not intrinsic rate constants - see equations 7 and 8 from Park et al., 2009 - also attached below). These surface areas do not seem to be routed in any measured of computed values. If I could determine how Park et al. arrived at these surface areas, I could integrate my script until the results of X1t match the measure concentrations I have determined for the major cations, silica, Al, and pH along the flow path in the aquifer I am studying. But with so many unknowns, I am at a loss of coming up with a reasonable approach to estimating the weathering reactions along the flow path. Please note, I just re-registered with my new University of Massachusetts Boston credentials. I spent the past 12 years at Tulane University and no longer receive emails via my tulane.edu email. Thus, my UMass email is the best way to reach me (karen.johannesson@umb.edu).Eqs 7 & 8 from Park et al.pdf Portion of Park et al.'s kinetic weathering script.pdf