Re: PHREEQC

["Elizabeth Delaney" <x99delaney1@xxxxxxxxxxx>]

David,

> What's the difference between what you did and what I did? Also, I don't

really understand what equilibrium phases does. My understanding is that it

is used to model how the minerals act in water at equilibrium under certain

conditions.

What does the manual say about EQUILIBRIUM_PHASES?

The manual says EQUILIBRIUM_PHASES is a way to input what the chemical saturation indices and concentrations will be at equilibrium. The output is the changes that must occur to reach this particular equilibrium.

Do you know what saturation indices are?

Saturation indices are the log of the ratio of the activity product of the compound to the solubility product constant of that same compound. The saturation idices have uses in determining whether something will precipitate out in water or not and, in some cases, how much will precipitate out.

What are the differences between these three simulations?

SOLUTION 1

EQUILIBRIUM_PHASES 1

Calcite 0 10

CO2(g) -2.0 10

END

SOLUTION 2

EQUILIBRIUM_PHASES 2

Calcite -1 10

CO2(g) -2.0 10

END

The differences between these two simulations are the changes in the saturation indices in the calcite at equilibrium. The concentrations stay the same.

SOLUTION 3

EQUILIBRIUM_PHASES 3

Calcite 0 0

CO2(g) -2.0 10

END

This third simulation is the again changes the satruation index of the calcite. The concentration is the same because the default is 10 moles.

> Then, the final question is, after the sea water and ground water

interaction have been taken care of, do I use equilibrium phases to add in

the limestone aquifer interaction? Thank you again for your help!

You tell me what you think and I'll comment.

 

Thank you again.

 

Elizabeth Delaney

Department of Chemistry

Western Michigan University

(269) 387-2926

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