Using SOLUTION_MODIFY in a coupled reactive transport

[omarchaabi]

Dear phreeqc users,

I am currently working on coupling IPhreeqc to a transport simulator. So far I have succeeded in validating the coupled simulator against IPhreeqc "example 11" where the water concentration is fixed at 1 Kg. However, for the intended study, water saturation will be changing over time in the transport simulator. I would like to ask if SOLUTION_MODIFY allows for modifying the mass/volume of water? Or is there any other way to go around this using IPhreeqc?

I have read in several posts that it would be more appropriate to use PhreeqcRM for reactive modeling. If there is no way around this for IPhreeqc does PhreeqcRM provide this option?

Regards,
Omar

[Pak]

There is no way around I think, but you can implement the same formulas that PhreeqcRM uses in your code. In the paper of PhreeqcRM is everything well explained, I think.

[dlparkhurst]

I think PhreeqcRM would be the better way to go. It allows changing porosity and saturation. You can look at the documentation for SetUnitsSolution https://water.usgs.gov/water-resources/software/PHREEQC/documentation/phreeqcrm/index.html for the way transport concentration units are converted to PHREEQC solutions (also GetConcentrations and SetConcentrations). Even if you continue to use IPhreeqc, the equations may be helpful.