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Kaushik Mitra

Thermodynamic Database for evaporation

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Hello,

 

I am currently working on modeling the precipitation of seawater under evaporation. I am particularly concerned with the Iron containing phases.

 

Which thermodynamic database should I choose to get a reliable result? "HMW" could have been an excellent choice except that it does not contain Fe. The other databases that are present include Fe as well as use B-dot equations. Generally B-dot is valid for Ionic Strengths less than 3 molal , but there were erroneous results (pg 132) cited in the book "Geochemical and Biochemical Reaction Modeling" by Craig Bethke. I am very perplexed with the choice of database. Please suggest a solution.

 

Thank you

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Hello Kaushik,

 

 

It would be best for you to modify the default thermo.tdat dataset. You should search literature for published datasets similar to Harvie-Moller-Weare model (Harvie and Weare, 1980)( Harvie et al.,1984). More recent publications might contain data on iron species.

 

Hope this helps,

 

Katelyn

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Hello Kaushik,

 

To clarify, you should use (not edit) the default thermo.tdat dataset for now. As far as ready-to-go datasets that come with the GWB, you will need to use a Debye-Huckel based thermo dataset, because there is no virial model dataset which contains iron. Of all the Debye-Huckel based methods, the B-dot (which thermo.tdat uses) is the best at higher ionic strength. However, as you mentioned be mindful as there is error involved. If you take a look at those references, you can find the information you will need (virial coefficients and information needed to calculate equilibrium constants).

 

Kind regards,

Katelyn

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