In Phreeqc, the "Saturation indices" section only presents the Saturation Index, Log Ion Activity Product, and Log K for each mineral. Is it possible to output the amount, relative amount, precipitate amount, or concentration of each mineral formed?
I have worked with the EQUILIBRIUM_PHASES function. Unfortunately, that function only works if you specify the mineral you want to model. Ultimately I would like to run a simple reaction and have the amount of each mineral calculated for each step.
Any insight into this issue is greatly appreciated!
https://www.usgs.gov › software › phreeqc-version-3
free download the software from this site.
Hi Jack,
Firstly, you need to be confident that your water composition is representative of the constituent concentrations and field conditions of the aqueous system you are studying.
Next when you speciate your input solution, what phases does PHREEQC predict will be under/over saturated? Some of these will be kinetically constrained so may not be present depending on your system. You will need to select phases which you think may be oversaturated and have the potential to precipitate. This will be an iterative process and you will need to document the influence a 'precipitating' phase has on your simulated system.
To simulate the precipitation of a phase you will need to use a combination of the Equilibrium Phases and User Print data blocks. In Equilibrium Phases detail your phases you want to precipitate with 0 moles present initially. You mention variable temperature, so do you need to also consider evaporation of water from the simulated system? User Print can be used to specify the mass (moles or mg/L, for example) of phase precipitated/removed from the system. Be sure to interrogate the output file in detail to see what effects are occurring when you precipitate a phase, do these effects appear reasonable?
I would suggest you look through the archived PHREEQC discussion threads on the USGS website:
https://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/mail
These threads provide further examples that may help you with your system development.
Unfortunately the other resource, the PHREEQC users group, no longer appears to active.
Good luck and best wishes,
Rebecca
SOLUTION 1 # NaHCO3 solution
temp 25
pH 7 charge
Na 2
C(4) 1
END
USE SOLUTION 1
REACTION 1
CaCl2 1
0.004 mol in 10 steps
EQUILIBRIUM_PHASES 1
Calcite 0 0
USER_PUNCH
-headings CaCl2_addition_mol Calcite_precipitation_mol/kgw
-start
10 PUNCH RXN
20 PUNCH EQUI("Calcite")
-end
SELECTED_OUTPUT
-reset false
-file Calcite_precipitation.txt
-user_punch true
END
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