Water Resources Applications Software

Geochemical || Ground Water || Surface Water || Water Quality || General

Summary of PHREEQE

       phreeqe - A program for geochemical calculations

       phreeqe [infile [ outfile [ database]]]

       infile - The name of the file in PHREEQE input format.
       outfile - The name of the file that will contain PHREEQE results.
       database - The name of the PHREEQE data base.

       If no arguments are specified, the program prompts for the input,
       output, and database file names.

       If only infile is specified, then outfile defaults to infile.out and
       the database to phreeqe.dat in the phreeqe2.4/bin_data directory.

       If only infile and outfile are specified, then the database defaults
       to phreeqe.dat in the phreeqe2.4/bin_data directory.

       PHREEQE is now obsolete and has been replaced with the program

       PHREEQE is a Fortran 77 computer program designed to model the
       chemical evolution of the aqueous phase as the result of specified
       geochemical reactions.  Based on an ion-pairing aqueous model,
       PHREEQE can calculate pH, redox potential, concentration of
       elements, molalities and activities of aqueous species, and mineral
       or gas mass transfer as a function of reaction progress.  The
       program is capable of simulating reactions due to mixing, titrating,
       net irreversible reaction, temperature changes, and mineral- or gas-
       phase equilibration.  The aqueous model, including elements, aqueous
       species, and mineral and gas phases, is exterior to the computer
       code and is completely user definable.  PHREEQE has been
       incorporated into several transport codes, including PHREEQM (Appelo
       and Willemsen, 1987, and Appelo and Postma, 1993).

       PHREEQE is a thermodynamic ion-association model.  Individual-ion
       activity coefficients and formation of aqueous complexes are used to
       account for deviations from a thermodynamically ideal solution.
       Extensions of the Debye-Huckel theory are used to calculate
       individual-ion activity coefficients.  The formation of each aqueous
       complex is defined by a mass-action expression with the appropriate
       association constant.  Equilibrium between the aqueous phase and a
       mineral or gas is defined by a mass action expression and a
       dissociation constant.  The program solves a simultaneous set of
       nonlinear equations that include some or all of the following
       equations:  an activity-coefficient equation for each aqueous
       species, a mass-action equation for each aqueous complex, mass-
       balance equations for each element in solution (except hydrogen and
       oxygen), a charge-balance equation, a redox-balance equation, a
       mass-action expression for each phase that is in equilibrium with
       the aqueous phase, an equation for ionic strength, and an equation
       for the activity of water.  The program primarily uses a Newton-
       Raphson approach to iteratively refine a solution to the
       simultaneous nonlinear equations.

       Version 2.4 1994/06/27 - WRDAPP tape 2.1 update release with
          enhancement that permits user to interactively page through
          output after execution is completed.

       Version 2.3 1994/05/20 - WRDAPP tape 2 release.

       Version January 1993 - Current version.  Inconsistencies with
          standards or programming style were identified by Fortran syntax-
          and structure-checking programs and corrected.  Changes included
          variable typing, structure of common blocks, use of generic
          functions, elimination of unused variables.

       Version August 1, 1990 - The linear equation solver was streamlined,
          parameter statements were added to facilitate redimensioning of
          the code, and unit numbers were stored in variables to facilitate
          installing the programs on PC's and other machines.  An
          interactive program, PHRQINPT, was published to facilitate data
          entry.  A high-ionic-strength version of the program was
          published, PHRQPITZ, that uses the specific-ion interaction
          approach to calculate activity coefficients.

       Version January 14, 1985 - Fortran 77 used.  Numerical method
          modified to correct an error in the formulation of the Jacobian
          matrix.  KNOBS keyword was added.  A new unit of concentration
          was accepted, mmol/kg solution.  An additional term in analytical
          expressions for log K was added.  The aqueous model for carbonate
          minerals and aqueous species was updated.

       Version November 1980 - Original release of program in Fortran 66.

       Proper use of the program requires adequate knowledge of
       geochemistry and a proper formulation of the problem.  Input is
       arranged in keyword data blocks, which can appear in any order.
       However, data fields for a keyword have a fixed format that is
       column dependent.  Use of the interactive program PHRQINPT to ensure
       proper formatting is suggested.  PHRQINPT has logic to ensure
       completeness of problem formulation and help for each item of input.
       The basic strategy for problem formulation is to define (1) a
       starting condition, that is a beginning solution composition(s)
       (SOLUTION keyword), (2) the irreversible reactions (IOPT(3),
       REACTION, STEPS keywords), and (3) reversible reactions (MINERALS

       PHREEQE and PHRQINPT are written in Fortran 77 with the following
       extensions: use of include files and variable names longer than 6
       characters.  Each program requires a minerals data base (provided)
       to be present in the directory from which they are executed.  Simple
       script programs are included to facilitate this.  Generally, the
       program is easily installed on most computer systems.  The code has
       been used on UNIX-based computers and DOS-based 386 or greater
       computers having a math coprocessor and 2 mb of memory.

       Parkhurst, D.L., Thorstenson, D.C., and Plummer, L.N., 1980,
          PHREEQE--a computer program for geochemical calculations: U.S.
          Geological Survey Water-Resources Investigations Report 80-96,
          195 p. (Revised and reprinted, 1990.)

       Fleming, G.W., and Plummer, L.N., 1983, PHRQINPT--an interactive
          computer program for constructing input data sets to the
          geochemical simulation program PHREEQE:  U.S. Geological Survey
          Water-Resources Investigations Report 83-4236, 108 p.

       Parkhurst, D.L., 1995, User's guide to PHREEQC--a computer program
          for speciation, reaction-path, advective-transport, and inverse
          geochemical calculations: U.S. Geological Survey Water-Resources
          Investigations Report 95-4227, 143 p.

       Plummer, L.N., Parkhurst, D.L., Fleming, G.W., and Dunkle, S.A.,
          1988, A computer program incorporating Pitzer's equations for
          calculation of geochemical reactions in brines: U.S. Geological
          Survey Water-Resources Investigations Report 88-4153, 310 p.

       Appelo, C.A.J., and Postma, D., 1993, Geochemistry, groundwater and
          pollution:  Rotterdam, Netherlands, and Brookfield, Vermont, A.A.
          Balkema.  (Contains description of input for PHREEQM.)

       Appelo, C.A.J., and Willemsen, A., 1987, Geochemical calculations
          and observations on salt water intrusions. I: A combined
          geochemical/mixing cell model: Journal of Hydrology, v. 94, p.

       Parkhurst, D.L., and Plummer, L.N., 1993, Geochemical models, in
          Alley, W.M., ed., Regional ground-water quality: New York, Van
          Nostrand Reinhold, chap. 9, p. 199-225.

       Plummer, L.N., 1984, Geochemical modeling: A comparison of forward
          and inverse methods, in Hitchon, B., and Wallick, E.I., eds.,
          Proceedings First Canadian/American Conference on
          Hydrogeology--Practical Applications of Ground Water
          Geochemistry, Banff, Alberta, Canada: Worthington, Ohio, National
          Water Well Association, p. 149-177.

       PHREEQE is no longer taught in any of the USGS National Training
       Center courses.

          U.S. Geological Survey
          David Parkhurst
          Denver Federal Center, MS 413
          Lakewood, CO  80227

          U.S. Geological Survey
          Hydrologic Analysis Software Support Program
          437 National Center
          Reston, VA 20192

       Official versions of U.S. Geological Survey water-resources analysis
       software are available for electronic retrieval via the World Wide
       Web (WWW) at:


       and via anonymous File Transfer Protocol (FTP) from:

         (path: /pub/software).

       The WWW page and anonymous FTP directory from which the PHREEQE
       software can be retrieved are, respectively:


       balninpt(1) - An interactive program for mass-balance
       netpath(1) - Interactive program for calculating NET
                    geochemical reactions and radiocarbon dating along
                    a flow PATH
       phreeqc(1) - A program for aqueous geochemical calculations
       phrqpitz(1) - A program for geochemical calculations in brines
       wateq4f(1) - A program for calculating speciation of major,
                    trace, and redox elements in natural waters

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