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B_Kimball

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  1. I am trying to estimate dissolved fluoride concentrations assuming a water sample is in equilibrium with both fluorite and calcite. This calculation gives me notably different total fluoride concentrations in GWB (~17 mg/kg F) and PHREEQC (~11 mg/kg F) when I use the wateq4f database for both programs. I have double checked to make sure the log K for fluorite solubility at 25 C is the same in both the GWB and PHREEQC versions of the database. Does anyone know why this discrepancy exists? Relevant files are attached. Thanks. fl_ca_1.txt fl_ca_1.sp8
  2. Thanks Brian. Your description of the "activity Kd model" does help. I have tried using both the Kd approach and a surface complexation model (SCM) to account for uranium attenuation along the flow path. In reference to a SCM, you said the magic words: "if you can parameterize it." I have the age-old problem of desiring more site-specific data to inform my SCM. When I try to incorporate a SCM with the FeOH+.sdat database and our estimates of HFO concentrations in the aquifer, the predicted attenuation of uranium is much lower than we observe in the field. A Kd model gets me closer to what we observe, but as you imply, these models are not ideal, especially when the pH of the system is changing. I will continue to think about this. Thank you.
  3. I am trying to model uranium attenuation in X1t using a simple Kd approach. I am using the Pb example and the associated Pb-Kd.sdat file as my template for this. The header of the Pb-Kd.sdat file states that the Kd value is given in units of mol/g solid. In other words, the sorbed concentration (mol/g) is provided instead of the actual Kd value (e.g., L/kg). Why is this the case? On a related note, is it possible to utilize the Kd approach in X1t using Kd values that change with the pH of the system? Thank you. Pb-Kd.sdat
  4. B_Kimball

    React only plotting Piper diagram

    Thanks Brian! It must have been the memory effect. I was able to get the plot I was aiming for.
  5. I updated to the latest version this morning. Now I'm finding that if I plot my results from a React run, I only have the option of a Piper diagram. When I open React-generated plots of constituents versus pH, made yesterday with the older version, they too open up as Piper diagrams. Any thoughts? Thank you.
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