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USCD1222 PHAST

PHAST, Calculation of isotope equilibrium constants for geochemical models

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1. NAME OR DESIGNATION OF PROGRAM:  PHAST.
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2. COMPUTERS
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Program name Package id Status Status date
PHAST USCD1222/01 Tested 07-JUL-2004
PHAST USCD1222/02 Tested 07-JUL-2004

Machines used:

Package ID Orig. computer Test computer
USCD1222/01 PC Windows PC Pentium
USCD1222/02 Linux-based PC,SUN Linux-based PC
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3. DESCRIPTION OF PROGRAM OR FUNCTION

The geochemical part of the program has the capability to perform a wide range of chemical reaction calculations that include aqueous complexation, mineral equilibria, surface complexation, ion exchange, solid-solution equilibria, gas-phase equilibration, and general kinetic reactions. In addition, geochemical simulations, which include all of these types of reaction calculations plus mixing, irreversible reactions, and temperature variation, may be used to define initial and chemical boundary conditions for the reaction-transport simulations. Essentially, any modeling capability available in PHREEQC may be used to establish initial and boundary conditions for the reactive-transport simulation of PHAST.
  
All spatially distributed properties are defined by zones that are rectangular prisms. Zones may overlap, in which case the order of definition is important because the last specification of a property for a cell or element will be the one used in the simulation. The units for input of properties may be a mixture of English and SI metric, however, all output data are SI metric with a user-selected time unit.
  
The transport part of PHAST is written in Fortran 90 and the geochemical part is written in C. Both parts dynamically allocate any computer memory necessary for program execution. Little effort has been expended to minimize storage requirements. Consequently, depending on the size of the domain, the program may require relatively large amounts of memory for execution.
  
In the application of PHAST, it is advisable to progress from simple to increasingly complicated simulations. First, the geochemical model PHREEQC should be used to evaluate chemical reactions by the use of reaction-path and then 1D-transport calculations. Second, PHAST should be used in flow-only mode to obtain an acceptable model of the flow system. Finally, PHAST should be used for reaction-transport calculations that combine the flow simulation with geochemical reactions.
  
PHAST is now in the beta-testing phase, and the source code is not available for general release. The documentation of the input files has been written, but a complete manual containing the theory and example calculations is not yet available.
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4. METHODS

March 24, 2004: PHAST version RC3 Released
Release Candidate 3 fixes a bug for rivers. If flux and river boundary conditions applied to the top of the grid, the river areas for each cell were not properly accumulated and the program failed.
An implicit method for integration of kinetic reactions has been added to the PHREEQC version that is included in PHAST. This method is more robust for stiff systems of ODE s. The next version of PHREEQC (2.9) will also include this alternative integration method. The implicit method is used when -cvode is included in a KINETICS data block of the chemistry data file, otherwise the usual Runge-Kutta method is used.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The keywords for transport have been devised for PHAST, but are based on input for the model HST3D (stripping out anything related to heat or density and using head in place of pressure). Most of the data blocks are related to the flow and transport parameters needed to simulate ground-water flow and solute transport.
  
The main interaction between the flow and transport data file and the chemical data file occurs in CHEMISTRY_IC (of the flow and transport data file), where entity numbers (solutions, equilibrium-phase assemblages, etc, as defined in the chemical data file) are assigned to spatial zones (rectangular parallelepipeds) to establish the initial conditions in the model domain. Note that it is possible to define initial conditions that change linearly in one of the coordinate directions for each zone (for example solution composition could vary linearly between two end members along the x coordinate direction for a zone).
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6. TYPICAL RUNNING TIME
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7. UNUSUAL FEATURES
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8. RELATED OR AUXILIARY PROGRAMS
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9. STATUS
Package ID Status date Status
USCD1222/01 07-JUL-2004 Tested at NEADB
USCD1222/02 07-JUL-2004 Tested at NEADB
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10. REFERENCES
USCD1222/01, included references:
- Donald C.Thorstenson And David L.Parkhurst:
Calculation of Individual Isotope Equilibrium Constants for Implementation In
Geochemical Models Water-Resources Investigations Report 02-4172
- David L. Parkhurst And C.A.J. Appelo:
User's Guide to PHREEQC (Version 2)- A Computer Program for Speciation,
Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations
Water-Resources Investigations Report 99-4259
USCD1222/02, included references:
- Donald C.Thorstenson And David L.Parkhurst:
Calculation of Individual Isotope Equilibrium Constants for Implementation In
Geochemical Models Water-Resources Investigations Report 02-4172
- David L. Parkhurst And C.A.J. Appelo:
User's Guide to PHREEQC (Version 2)- A Computer Program for Speciation,
Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations
Water-Resources Investigations Report 99-4259
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11. HARDWARE REQUIREMENTS
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
USCD1222/01 FORTRAN+C
USCD1222/02 FORTRAN+C
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13. SOFTWARE REQUIREMENTS
USCD1222/01
Windows

USCD1222/02
Linux/Solaris
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS
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15. NAME AND ESTABLISHMENT OF AUTHORS

David L. Parkhurst
U.S. Geological Survey, WRD
Denver Federal Center, MS 418
Lakewood, CO 80227
USA
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16. MATERIAL AVAILABLE
USCD1222/01
Files for PC Windows platforms:
documentation, examples, source files, tests and auxiliary program "Model
Viewer"

USCD1222/02
Files for Linux, Sun workstations:
documentation, examples, source files, tests
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17. CATEGORIES
  • R. Environmental and Earth Sciences

Keywords: aqueous solutions, geochemistry, ground water, specifications.