HYDROGEOCHEM 2 - reactive multispecies-multicomponent chemical transport model - hydrologic transport and mixed geochemical kinetic/equilbrium reactions in saturated/unsaturated media
HYDROGEOCHEM 2 Categories: hydrogeochemical models, reactive transport, geochemical models, solute
transport models - saturated zone, solute transport models - unsaturated zone
HYDROGEOCHEM 2 Description
HYDROGEOCHEM 2 is a modification of HYDROGEOCHEM 1.0 (Yeh et al., 1991), a general purpose computer program written in FORTRAN 77 which was designed to solve coupled hydrologic transport and geochemical equilibrium problems. The modification includes replacement of the EQMOD chemical equilibrium subroutines by a mixed chemical Kinetic and Equilibrium model (KEMOD) to deal with species whose concentrations are controlled by either thermodynamics or kinetics.
HYDROGEOCHEM 2 is a coupled model of hydrologic transport and geochemical reaction in saturated-unsaturated media. HYDROGEOCHEM 2 comprises two basic modules: the transport module and the geochemical reaction module. The transport module is designed to simulate: (1) transient and/or steady-state transport of Ns aqueous components, (2) transient and/or steady-state mass balance of Ns adsorbent components and NSITE ion-exchange sites. The geochemical reaction module is designed to compute the species distribution of N = (Na+ Ns) component species, Mx-Kx equilibrium-controlled complexed species, (My – Ky) equilibrium-controlled adsorbed species, Ky kinetic-controlled adsorbed species, (Mz – Kz) equilibrium-controlled ion-exchanged species, Kz kinetic-controlled ion exchanged species, (Mp – Kp) equilibrium-controlled potentially-precipitated species, and Kp kinetic-controlled precipitated species. The two modules are solved iteratively with three options: (1) a complete iteration, (2) an operator splitting, and (3) a predictor-corrector method. The transport module includes advection, dispersion/diffusion, and slight deformation. In the geochemical reaction module, nine types of reactions are included to generate the aforementioned eight types of product species.
HYDROGEOCHEM 2 is designed for generic application to reactive transport problems controlled by both kinetic and equilibrium reactions in subsurface media. Input to the program includes the geometry of the system, the spatial distribution of finite elements and nodes, the properties of the media, the potential chemical reactions, and the initial and boundary conditions. Output includes the spatial distribution of chemical concentrations as a function of time and space and the chemical speciation at user-specified nodes.
The program must be run with a consistent set of units. Units of mass (M), length (L), and time (T) are indicated in the input description. The unit of length should be decimeter (dm), and the unit of mass for any chemical species should be mole. The density of water and solid should be expressed in kg/dm3 (liter). The ion-exchange capacity is in equivalents/Mass of solid. The corresponding concentration unit of all species (aqueous, sorbed, and precipitated species) is mole/liter of fluid (Molar); the corresponding unit for the sorption distribution coefficient is dm3/kg (= ml/g). Any units of time may be used as long as the same unit is used throughout the input file.
HYDROGEOCHEM 2 is the only commercially-available model for the simulation of reactive multispecies-multicomponent chemical transport controlled by both kinetic and equilibrium reactions.
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HYDROGEOCHEM 2 Manual - Part 2 (pdf file)
HYDROGEOCHEM 2 Manual - Part 1 (pdf file)
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