This application example includes gypsum, liquid water, and vapor, dissolved and gaseous air, calcium and sulfate (main components of gypsum besides water) and two conservative species, potassium and chloride (see Table 2). It also considers the occurrence of anhydrite, which may precipitate as a result of gypsum dehydration. Note that the coexistence in equilibrium of anhydrite and gypsum can fix water activity and therefore produce invariant points (Risacher & Clement 2001). As was shown above, to our knowledge, PROOST is the first multiphase reactive transport capable of modeling this scenario.
Table 2
Chemical species and reactions considered
| H2O(l), H2O(g), air(l), air(g), Ca, SO4, K, Cl, gypsum, anhydrite |
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| H2O(l), H2O(g), air(l), air(g), Ca, SO4, K, Cl, gypsum, anhydrite |
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