PHRQPITZ is a computer program capable of making geochemical calculations in brines and other electrolyte solutions of high concentrations using the Pitzer virial-coefficient approach for activity-coefficient corrections. Reaction-modeling capabilities include calculation of (1) aqueous speciation and mineral-saturation index, (2) mineral solubility, (3) mixing and titration of aqueous solutions, (4) irreversible reactions and mineral-water mass transfer, and (5) reaction path. The computed results for each aqueous solution include the osmotic coefficient, water activity, mineral saturation indices, mean activity coefficients, total activity coefficients, and scale-dependent values of pH, individual-ion activities and the individual-ion activity coefficients. A data base of Pitzer interaction parameters is provided at 25 C for the system: Na-K-Mg-Ca-H-Cl-SO4-OH-HCO3-CO3-CO2- H2O, and extended to include largely untested literature data for Fe(II), Mn(II), Sr, Ba, Li, and Br with provision for calculations at temperatures other than 25 C. An extensive literature review of published Pitzer interaction parameters for many inorganic salt is given.

The interactive preprocessor PITZINPT is included with PHRQPITZ. The program results are saved in a text file. PHRQPITZ is a public domain program, distributed by IGWMC with source code, DOS-based runtime versions and example data sets. The user's manual consists of installation instructions and PHRQPITZ documentation.

SYSTEM REQUIREMENTS

Intel 80386/80486 based computer with math coprocessor, 4 Mb RAM, hard drive with at least 1 Mb free disk space, DOS 3.0 or higher.

Authors: L.N. Plummer, et al. (U.S. Geological Survey).