| Chemical Equilibrium Models (MINEQL+ & MINTEQA2) | |
| MINEQL+ is an user-friendly modeling program to model chemical equilibrium, whereas MINTEQA2 can be used to model geochemical equilibrium speciation
for dilute aqueous systems. For example, MINTEQA2 can be used to calculate the equilibrium composition of dilute solutions in laboratory or natural aquatic systems. It can be used to calculate the mass distribution between dissolved,
adsorbed, and multiple solid phases under a variety of conditions. The thermodynamic database in both programs are identical.
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| Aqueous Geochemistry Calculations (PHREEQC) | |
| PHREEQC is a computer program designed to perform a wide variety of aqueous geochemical calculations.
PHREEQC is based on an ion-association aqueous model and has capabilities for (1) speciation and saturation-index calculations; (2) reaction-path and advective-transport calculations involving specified
irreversible reactions, mixing of solutions, mineral and gas equilibria, surface-complexation reactions, and ion-exchange reactions; and (3) inverse modeling, which finds sets of mineral and gas mole transfers that account for composition differences between waters, within specified compositional
uncertainties.
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| Brine Reactions (PHRQPITZ) | |
| PHRQPITZ is a modification of the geochemical modeling code PHREEQC to permit calculations of geochemical
reactions in brines and other highly concentrated electrolyte solutions using the Pitzer virial-coefficient approach for activity-coefficient corrections.
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| Aqueous Geochemistry Calculations (WEB-PHREEQ) | |
| WEB-PHREEQ is an implementation of the geochemical modeling code PHREEQC on the world wide web. Using a forms-based
interface, one can calculate equilibrium concentrations (or activities) of chemical species in solution, and the saturation indices of solid phases in equilibrium with it, from a real or hypothetical chemical analysis. The model supports selected gases, setting phases at a desired saturation
with respect to the solution, changing the solution's temperature, Eh, or pH, allowing the pH to be fixed or variable. Not all the features of PHREEQC are implemented. Those seeking full flexibility
should use the UNIX or DOS versions of PHREEQC.
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B. Saini-Eidukat, North Dakota State University
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