Applications and Case Studies > Groundwater flow studies

Leaching

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Sergio:
Hello everyone.
I would like to understand how can I use the PHREEQC to obtain results about leaching of a solid sample with the concentrations below (ppm):
Cd 0,005; Cr 0,007; and others...
How can I put the element if there is not in the datebase, for example Ag.
My goal is understand the interactions between water and that sample, inside the soil, after mixing, and if there will be changes of pH and pE. I need to know if the changes of pH and pE aftermath in some new ionic elements in these enviroment aqueous. If Cr+3 can be Cr+6 in some cases.
Ask me if someone need more information. Right?
Thanks a lot. I'm waiting for their response.

dlparkhurst:
Most databases have NO3-, which is defined in SOLUTION_MASTER_SPECIES as N(5).

Ag is in wateq4f.dat, llnl.dat, minteq.dat, and minteq.v4.dat. You can use them for examples for ion-association aqueous models. Ag is also in sit.dat, the specific-ion interaction aqueous model.

If you are concerned with pH and pe, you probably need to look at the major element reactions (including iron). Reactions with these elements are most likely to control the chemistry of your setting. If you have water chemistry for water that has reacted with your rock, it is possible to use INVERSE_MODELING to try to figure out the major reactions.

Trace metals are going to be difficult to model with PHREEQC because they are unlikely to be derived from pure phases or form pure phases. Known stoichiometry is needed for INVERSE_MODELING and the stoichiometry of the reactive part of the source rock may be difficult to know for trace elements. Likewise sorption or incorporation as trace constituents in precipitates are likely to affect trace element concentrations. Although SURFACE and SOLID_SOLUTION can treat some of these processes, they may not be appropriate or you may not have the thermodynamic data (log Ks) that you need.

Sergio:
Is possible to do study hydrogeochemistry with my sample in this software? I have Ag+, Cr+, Cl-, Ca+2.
What the dynamic interactions these elements of my sample and water. I know that I will have Ca(OH)2 for example. But I need to know if will appear another thing. I dont know yet.
Do you have any examples that I can use to obtains results something like that?
Do you have another examples how I can put Ag in my research?
Thanks again

dlparkhurst:
I do not know if geochemical modeling is the right approach for your study. If you have chemical analyses, start by calculating saturation indices of minerals. That will give you an indication of whether minerals should dissolve or precipitate, or perhaps are reacting fast enough to maintain equilibrium.

Sergio:
How can I obtain wateq4f.dat, minteq.dat and others. I need to use Ag and Cr. And they are not in database.

Send me more examples for my study. Please. I need to learn more and more about prhreeqc.

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