HYDOGEOCHEM is a coupled model of HYDROlogic transport and GEOCHEMical in saturated-unsaturated media. It is designed to simulate transport of Na, aqueous component and transient and/or Steady-State mass balance of Ns adsorbent component and ion-exchanges sites. Along the transport path, HYDROGEOCHEM computes the species distribution of N component species, Mx complexd species; my absorbed species, M, ion-exchanged species, and Mp potentially precipitated specie. The physical, hydrological and chemical setting as follows.
-Media: Heterogeneous and Anisotropic..
-Flow Conditions: Saturated-Unsaturated.
-Hydrologic Processes: Advection, Dispersion and Diffusion.
-Chemical Processes: Aqueous Complexation, Adsorption/Desorption (Surface Complexation, Constant Capacitance, and Double Layer Approaches), Ion-Exchange, Precipitation/ Dissolution, Redox Acid-Base Reactions.
-Source/Sink: Spatially: Temporally Dependent Element and Pont Sources/Sinks.
-Initial Conditions: Prescribed Initial Condition or the Simulated Steady-State Solution as the Initial Condition.
-Boundary Conditions: Prescribed Total Analytical Concentrations on Dirichlet Boundaries, Prescribed Fluxes on Flow-In Boundaries, Natural Advective Fluxes on Flow-Out Boundaries—All Boundary Values (Concentrations or Fluxes) are Spatially and Temporally Dependent.
-Numerical Discretization: Finite-Element Methods with Quadrilateral Elements, Triangular Elements, or the mixtures of theses two types.
-Approximation Options: Consistent Matrix or Mass Lumping Nodal Quadrature or Gaussian Quadrature for Surface and Element Integrations.
-Solvers: Direct Ban Matrix Solver Basic Point Interactions, and four PCG methods (Polynomial PCG, Incomplete Cholesky PCG, Modified Incomplete Cholesky PCG, and Symmetric Successive Over-Relaxation PCG).
-Time Stepping: Implicit Difference/Crank-Nicholson Central Difference/Mid-Difference.
-Solution Methods for Geochemical Reactions: Newton-Raphson with Full Pivoting to Solve the Jaccobian Matrix Equation and Constraints on Species Concentrations.
HYDROGEOCHEM is the only commercially available model for the simulation or reactive multispecies- multicomponent chemical transport through saturated-unsaturated media. It is not a path model; it is a true transport model coupled with homogeneous and heterogeneous geochemical reactions.