metalloid release from pure mineral phaase calculations

[jnc]

I am new to use geochemists workbench and wondering if there is a way that I can calculate the expected concentration of ions released from mineral phases under specific redox and pH conditions. I would like to determine whether the dissolution of stibnite is controlling the release of Sb in my soil porewater solutions. Ideally, I would like to input initial soil concentration with specific redox and pH values for different time points, and see if these values are similar to measured samples. 
Thank you

[Jia Wang]

Hello Jnc,

Here are a couple of suggestions to help you get started. You might want to get started by familiarizing using SpecE8 to calculate the equilibrium speciation of your fluid. To do so, start by setting up the basis pane with using your initial soil fluid species concentrations. To add basis species, click the ‘add’ button on the bottom left of the basis pane. To include redox conditions, such as Eh, you will need to swap in e into your basis pane. To include the pH of your fluid, add in ‘H+’ from the dropdown menu. To calculate the equilibrium concentration of Sb-species in solution, you can select the basis species containing Sb and swap in Stibnite. For more information, please refer to section 7 SpecE8 in the GWB Essentials Guide.

Just note that the default thermo.tdat does not include stibnite thermodynamic data. You can modify the dataset to add stibnite and related Sb-species to the dataset using literature values. A good place to start may be the thermo.com.V8.R6+.tdat, an expanded variant of the Lawrence Livermore National Lab database. This thermo database does contain data for stibnite and Sb(OH)3(aq) as a basis species. You can edit thermo dataset using a text editor or use GWB's graphical thermo data editor, TEdit app.  For more information, please see section 9 Using TEdit in the GWB Essentials Guide.

Hope this helps,

Jia Wang