Transport of charge balance when coupling with a multicomponent transport code

[sbai.github]

Hello All,

I have read in the following paper by Parkhurst and Wissmeier (2016) (https://doi.org/10.1016/j.advwatres.2015.06.001) that for a component-based reactive transport simulation, one needs to transport the charge balance component using advection and mechanical dispersion and/or diffusive transport processes.

1- During this process should we keep the negative sign of the charge balance in all model cells?
2- If not, what are the expected side effects? could you explain?

Thank you in advance,
Best

[dlparkhurst]

If you use charge-balanced solutions and charge-balanced surfaces, it may not be necessary to transport the charge. However, I recommend that you use it as one of your transported components. You should keep the quantity and sign of the charge for each cell, positive or negative, as it is provided by PhreeqcRM.

If you do have charge imbalances, and you do not transport the charge, you could have unexpected reactions, particularly for pH and redox. If you used real analyses as your initial conditions with their inevitable charge imbalances, you would get unreliable results.