Surface precipitation?

[Charlie]

Q. Is it possible to include surface precipitation as well in PHREEQ-C (accounting for the phenomenon that near the surface concentrations may be high enough for precipitation whereas overall solution concentrations are too low for precipitation to occur).

A. Basically, no, I did not implement Dzombak and Morel's surface precipitation model.
There are solid solution capabilities and general kinetics capabilities. It might be possible to use them to try to recreate the effects of surface precipitation, but it would not be straightforward.

Answer by D. Parkhurst.  (Edited from http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/mail/msg00142.html)