Mattm

Hey Karen, I was attempting to input the above script into my model, and I stumbled across a "node by node" function in the mineral "mass" box. If you select "node by node", where you select "volume%" as your units, you can change the volume percent of the mineral in each node of your model. Maybe this was part of a recent update. Cheers,

Hello, I'm putting a reactive transport model together in X1t. The aquifer I'm modeling contains carbonates, clays, and silicates. I'm utilizing custom kinetic rate laws which are sensitive to changes in pH. I have been trying to run simulations using kinetic constraints for all the minerals, but my model has been getting stuck and crashing and/or running incredibly slow. I have read that it is best to avoid simultaneously using kinetic constraints for minerals with greatly differing kinetic rates, and it is a better approach to instead set the more rapidly reacting minerals as equilibrium species. I'm wondering how I might do that? Does that mean I would just add the rapidly reacting minerals as "simple" minerals? Since the "simple" minerals are "added to the model over the course of the simulation", I'm not sure how I would approach setting their wt% values with respect to the single wt% value I have from XRD data. Likely, I am misunderstanding the meaning of the "simple" minerals. I'm also wondering, at what point do I draw the line? For example, I am including carbonates with reaction rates around 10^-5, chlorite with a reaction rate around 10^-12, anorthite with a reaction rate around 10^-14, and clays with reaction rates as low as ~10^-20 in basic conditions. I think I should be using equilibrium to model carbonate and perhaps chlorite dissolution, but between anorthite and the clays, I still have several orders of magnitude difference in their kinetic rates. I guess my question is at what difference in kinetic rate magnitude would you avoid utilizing kinetics. Thanks

Hi Jia, Thanks for the reply. It turns out I had a few settings set up kind of wrong. But, ultimately, I determined that the reason the software kept crashing (without reading any errors - just closing down) was because my CPU was slightly overclocked. I returned my CPU to factory settings, then the software now runs the models! Not sure how that works. Cheers,

Hello, I'm a grad student attempting to put together a reactive transport model in X1t. The goal is to construct a 2D reactive transport model to simulate groundwater chemical evolution in a substrate in my study area. My supervisor recommended starting in React and then working my way into X1t and then X2t, when I can get the previous simulations to run and follow the chemical trends I'm after. My model includes clays, feldspars, carbonates, chlorite, and pyrite. I have XRD results to support wt% values for mineral species, and I'm using a series of kinetic reaction equations composed by my supervisor (which he gathered from reputable research). I got the model to run and follow the ion trends I have for 11 groundwater samples oriented along a flow path, using React. Now, I'm attempting to put together a 1D reactive transport model with the same setup. For my initial solution, I'm using a mixture of the 11 samples I have (seems like an okay idea), and I'm flushing into the model a groundwater sample that represents a relatively fresh (low TDS) groundwater sample from elsewhere in my dataset. I got the model to run without pyrite with some okay results. My issue is that I can't get the model to run if I include kinetic pyrite (0.03 wt%). I think it's because I'm not starting with good initial redox conditions and the model can't converge because oxygen fugacity is shooting off somewhere, but I'm not sure. Inevitably X1t crashes, unless I start with an initial oxygen partial pressure of approximately 2 atm! I guess my foremost question is how you recommend setting initial redox conditions. The aquifer I'm attempting to simulate is overlain by glaciolacustrine sediments, often tens of metres thick, so dissolved oxygen content is low. But, the lower of a value I use for initial oxygen fugacity, the quicker the model crashes. I can get the model to run with "simple" pyrite, but I'm not sure if it is logical to keep adding pyrite at every step of the simulation. One other thing I'm wondering about is how to plot saturation index plots in Gtplot from data in GSS. This seems like a trivial task, and I've put together dozens of scatter plots in Gtplot, but I can't get the same values I have in my GSS spreadsheet to plot in Gtplot. I have Log(Q/K) values in GSS that hover around saturation with respect to calcite, but when I plot them in Gtplot, no matter what style of axes I use, it shows SI values up to 10. Attached is my X1t file, GSS spreadsheet of the samples oriented along the east-west flow path I'm trying to simulate, and I'll include a picture of the trends I'm trying to simulate. I've been at this for a few weeks, so any help would be greatly appreciated. Reactive transport model 1D.x1t Groundbirch PV samples.gss