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Adding elements to data base
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Topic: Adding elements to data base (Read 1348 times)
Franco Galarce
Contributor
Posts: 8
Adding elements to data base
«
on:
January 20, 2021, 12:07:43 AM »
Hi,
I need to obtain the saturation index of the mineral species that should be present in a geothermal system, asumming the thermodynamic equilibrium. I only have the geothermal fluid data at 260°C, and there are certain elements that are not including in the lnll data base. That elements are: SiO2, Rb, Cs, Sb, and As. How can I add them?
I also have doubts about how to get the "pe" parameter from pH value. I chose -5 to test.
This is my input:
SOLUTION 1
temp 260
pH 6.98
pe -5
redox pe
units mg/l
density 1
Alkalinity 34 as HCO3
B 273
Br 10.4
Ca 543
Cl 10066
F 10.9
K 871
Li 59
Mg 0.17
Na 5182
S(6) 22
Sr 13.4
-water 1
END
Regards!
Franco G.
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dlparkhurst
Top Contributor
Posts: 3086
Re: Adding elements to data base
«
Reply #1 on:
January 20, 2021, 01:32:35 AM »
All of those elements are included in llnl.dat. Check the first line of the output for the database that you are using.
I got an error when I ran your file because of the Alkalinity definition. Apparently there was more alkalinity from B, Si, etc than the defined alkalinity, so the program failed. If you use C(4) instead of Alkalinity, it should work.
As for pe, the main element that it affects is As. If you know the redox state of As, you can define it [As(3), for example].
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Franco Galarce
Contributor
Posts: 8
Re: Adding elements to data base
«
Reply #2 on:
January 22, 2021, 07:45:11 PM »
Hi,
How can I input SiO2? For example, I have 531 mg/l of SiO2, so I have to input the 87,5% of this value as Si?
Regards
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dlparkhurst
Top Contributor
Posts: 3086
Re: Adding elements to data base
«
Reply #3 on:
January 22, 2021, 09:19:25 PM »
The default gram formula weight for converting mass to moles in the llnl.dat database is the gfw of SiO2 (defined in the SOLUTOIN_MASTER_SPECIES data block of the database).
You can also ensure a specific formula or gram formula weight in SOLUTION input
Code:
[Select]
SOLUTION
Si 531 as SiO2
Look at the description of SOLUTION in the manual for more details.
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Franco Galarce
Contributor
Posts: 8
Re: Adding elements to data base
«
Reply #4 on:
January 27, 2021, 11:25:07 PM »
Thanks!
I have another question. How can I introduce an equilibrium with andesite-dacite minerals....?
- Plagioclase
- Amphibole
- Biotite
Those minerals are not in the llnl database. There are albite, tremolite, and annite, but I need the solid solutions. I was able to introduce the rest of minerals (Quartz, K-feldespar, etc), but not those.
Regards.
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dlparkhurst
Top Contributor
Posts: 3086
Re: Adding elements to data base
«
Reply #5 on:
January 28, 2021, 03:15:42 AM »
I tend to avoid thermodynamic data issues You can start with the other databases. phreeqc.dat has a K-mica. Databases have data for Albite and Anorthite, so maybe there are some solid solution models to get K for a given composition. I'm not sure how much effort is reasonable because equilibrium may be suspect anyway.
One issue is that llnl.dat uses SiO2(aq) for the master species, whereas the other databases use H4SiO4, so you may have to rewrite the equations for whichever master species you are using.
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