1. General Model Information

Name: PHREEQC - A program for aqueous geochemical calculations

Acronym: PHREEQC


Main medium: terrestrial
Main subject: geochemistry
Organization level: ecosystem
Type of model: partial differential equations, ordinary differential equations
Main application:
Keywords: cation exchange, anion exchange,surface-complexer, irreversible reactions ,solution composition, speciation, reaction-path, advective-transport, inverse problem, geochemical calculations ,Ag, Al, As, B, Ba, Br, C, Ca, Cd, Cl, Cs, Cu, F, Fe, Fulvate, H, Humate, I, K, Li, Mg, Mn, N, Na, Ni, O, P, Rb, S, Se, Si, Sr, U, Zn.

Contact:

David Parkhurst
U.S. Geological Survey
Denver Federal Center, MS 413
Lakewood, CO 80225
email: dlpark@usgs.gov

Point of contact for PHREEQCI:
U.S. Geological Survey
Hydrologic Analysis Software Support Program
437 National Center
Reston, VA 20192
email: h2osoft@usgs.gov

Author(s):

Parkhurst, D.L. and others (PHREEQC)
Charlton, S.R., Macklin, C.L., Parkhurst, D.L(PHREEQCI)

Abstract:

PHREEQC is a computer program written in the C programming language that is 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.

METHOD
PHREEQC is derived from the Fortran program PHREEQE, but it has been completely rewritten in C with the addition of many new capabilities. New features include the capabilities to use redox couples to distribute redox elements among their valence states in speciation calculations; to model ion-exchange and surface- complexation reactions; to model reactions with a fixed-pressure, multicomponent gas phase (that is, a gas bubble); to calculate the mass of water in the aqueous phase during reaction and transport calculations; to keep track of the moles of minerals present in the solid phases and determine automatically the thermodynamically stable phase assemblage; to simulate advective transport in combination with PHREEQC's reaction-modeling capability; and to make inverse modeling calculations that allow for uncertainties in the analytical data. The user interface is improved through the use of a simplified approach to redox reactions, which includes explicit mole-balance equations for hydrogen and oxygen; the use of a revised input that is modular and a completely free format; and the use of mineral names and standard chemical symbolism rather than index numbers. The use of C eliminates nearly all limitations on array sizes, including numbers of elements, aqueous species, solutions, phases, and lengths of character strings.

A new equation solver that optimizes a set of equalities subject to both equality and inequality constraints is used to determine the thermodynamically stable set of phases in equilibrium with a solution. A more complete Newton-Raphson formulation, master- species switching, and scaling of the algebraic equations reduce the number of failures of the numerical method in PHREEQC relative to PHREEQE.

PHREEQCI is a Windows-based graphical user interface for the geochemical computer program PHREEQC. It is a separate program that includes the PHREEQC program. PHREEQC is a multipurpose geochemical program than can perform speciation, inverse, reaction-path, and 1D advective reaction-transport modeling. PHREEQCI provides the capability to generate and edit input data files, run simulations, and view text files containing simulation results, all within the framework of a single interface. A built-in help facility contains the complete manual to PHREEQC that can be viewed with an HTML browser, such as Netscape or Internet Explorer.


II. Technical Information

II.1 Executables:

Operating System(s):
PHREEQCI compiled for
Microsoft Windows 3.x, 9x, or NT (4.6MB) [Europe] (4.6MB)

PHREEQC compiled for...
Data General AViiON (1.0MB)
Sun SPARCstation (Solaris) (1.0MB)
IBM-compatible PC, 386 or higher with math coprocessor (1.3MB)
IBM-compatible PC, 386 or higher with math coprocessor (includes source) (1.4MB)

II.2 Source-code:

Programming Language(s): C
PHREEQCI source code for compilation under...

Microsoft Windows 3.x, 9x, or NT (429K) [Europe]
The above software can also be accessed via anonymous FTP from water.usgs.gov or www.geogr.uni-jena.de in the /pub/software/geochemical/phreeqci directory.
PHREEQC
source code for compilation under...

UNIX (1.0MB) [Europe]

DOS (1.3MB)

II.3 Manuals:

PHREEQCI for Windows Manual:
User's Manual, PostScript (677K)
User's Manual, Portable Document Format (PDF) (83K)

PHREEQC Manual:
User's Guide, PostScript (PS) (1.3MB)
User's Guide, Portable Document Format (PDF) (753K)

II.4 Data:

DATA REQUIREMENTS 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. Data fields for a keyword are read in a free format, thus they are not column dependent.

For speciation modeling, analytical data for a solution composition (SOLUTION keyword) are needed.

For reaction-path modeling the following data are needed: (1) initial conditions: initial solution composition (SOLUTION keyword), initial exchanger composition (EXCHANGE keyword), surface-complexer composition (SURFACE keyword), and the identity and amounts of each phase that may react to equilibrium (EQUILIBRIUM_PHASES keyword) and (2) definition of the irreversible reactions (REACTION, MIX, and REACTION_TEMPERATURE keywords).

For 1D advective transport modeling, all the data for reaction-path modeling are needed for each cell in the modeled system.

For inverse modeling, the solution composition of the final solution and one or more initial solutions are needed (SOLUTION keyword). In addition, the identity and composition of a set of plausible reactants and products are needed.

Two default databases are included that contain the definition of a set of aqueous species, exchange species, surface species, and mineral and phases for the elements: Ag, Al, As, B, Ba, Br, C, Ca, Cd, Cl, Cs, Cu, F, Fe, Fulvate, H, Humate, I, K, Li, Mg, Mn, N, Na, Ni, O, P, Rb, S, Se, Si, Sr, U, Zn. If additional elements, species, or phases are needed, then chemical reactions, log K, and data for the temperature dependence of log K are needed for each additional species and phase.



III. Mathematical Information


III.1 Mathematics


III.2 Quantities


III.2.1 Input

III.2.2 Output


IV. References

Charlton, S.R., Macklin, C.L. and Parkhurst, D.L., 1997, PHREEQCI--a graphical user interface for the geochemical computer program PHREEQC: U.S. Geological Survey Water-Resources Investigations Report 97-4222, 9 p.
PostScript (677K) PDF (83K)

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. (Included in the phreeqc doc subdirectory of the software distribution package as PostScript, manual.ps, and Acrobat, manual.pdf, formatted files.)
PostScript (PS) (1.3MB) PDF (753K)

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., 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.)

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.

Plummer, L.N., Prestemon, E.C., and Parkhurst, D.L., 1991, An interactive code (NETPATH) for modeling NET geochemical reactions along a flow PATH: U.S. Geological Survey Water-Resources Investigations Report 91-4078, 227 p. Plummer, L.N., Prestemon, E.C., and Parkhurst, D.L., 1994, An interactive code (NETPATH) for modeling NET geochemical reactions along a flow PATH--version 2.0: U.S. Geological Survey Water- Resources Investigations Report 94-4169, 130 p.


V. Further information in the World-Wide-Web

USGS geochemical models [USA]
USGS geochemical models [Europe]

VI. Additional remarks


Last review of this document by: T. Gabele: 28. 10. 1998
Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:47 CEST 2002

Go back to Register of Ecological Models (R E M)