Hi Brian:
Per our discussion, I am submitting my questions through the forum.
I am trying to use the geobench to direct an in-situ remediation for cadmium. Calcium polysulfide (CaS5) will be injected to the ground. The injection solution will have 54 gram per liter of concentration. At the injection point, the concentration of CaS5 will have the concentration of the injection solution. At the injection radius of influence edge (i.e. 10 ft from the injection point), the concentration of CaS5 levels will be reduced to several orders of magnitudes lowers.
My goal is to figure out:
The site-specific Eh-Ph diagram under the different CaS5 concentrations.
The sulfide concentration at which sulfide can not effectively precipitate cadmium.
First step:
I read the user guidance and forum and conduct the modeling follow the step
Input two sets of parameters in Spec8 as show in the attached file “S1-full” and “S7-full”:
Note that:
S1 is the simulation of the condition near the injection location and CaS5 concentration is the injection solution level.
S7 is the simulation of the condition away from the injection location and CaS5 concentration is only 1/1000 of the injection solution.
The input requires pH and O2 level in the aquifer, the level of the reagent (CaS5) really determine the pH and O2 levels and I can not assume the constant pH and O2 levels. I used the pH and O2 level measured in the field.
Second step:
I used the output of the log activities from SpecE8 files and directly applied the log activities to the Act2 input activities for different constituents. See the attached in-put Act 2 files: S1-input and S7-input.
Please help me answer:
Is it Ok to use the Spec8 log activities output file directly? If not, please direct me how to generate the correct activities?
I selected a few constituents that show highest log activities to the Act 2. Meanwhile, when Ca++ and CaSO4 both showed high log activities, I used the constituent with high log activities – CaSO4 as the input for calcium. Please let me know whether this is an appropriate procedure?
Because CaS5 really change pH, ORP, and DO levels, I changed pH and O2 level in the Spec8. Is there way to actually estimate the CaS5 concentrations and corresponding pH and oxygen level? or I should just use the site background pH and DO levels?
Lastly, which program can directly estimate sulfide concentration at which sulfide can not effectively precipitate cadmium anymore – meaning the aqueous concentration will be more than 0.003 ug/L.
Thank you!
s7-full.sp8
s1-full.sp8
S1-input.ac2
S7-input.ac2
