Aquifer : aqu

The Aquifer or Saturated Zone component of FRAMES models solute transport through the ground water environment (i.e., partially saturated and saturated zones). Specifically, this component provides estimates of ground water constituent fluxes at various transporting medium interfaces (e.g., water table or aquifer/river interface) and constituent concentrations at withdrawal wells. Constituent fluxes at transporting medium interfaces represent boundary conditions for the next medium in which constituent migration and fate is to be simulated (e.g., groundwater contamination entering a surface-water environment). Constituent concentrations at withdrawal wells provide constituent levels for the exposure assessment component of FRAMES.

The migration and fate of constituents through the groundwater environment are described by the three-dimensional, advective-dispersive equation for solute transport. The results are based on semianalytical solutions (i.e., solutions that require numerical integration) that are well established in the scientific literature. To increase computational efficiency, limits of integration are also identified.

The Saturated Zone module accounts for the major mechanisms of constituent mobility (i.e., adsorption/desorption), persistence (i.e., degradation or decay), advection, and hydrodynamic dispersion. Mobility is described by an equilibrium coefficient that assumes instantaneous adsorption/desorption between the soil matrix and the pore water. Persistence is described by a first-order degradation/decay coefficient. Radionuclide decay products are also accounted for. Advection is described by constant, unidirectional flow in the vertical direction in the partially saturated (vadose) zone and in the longitudinal direction in the saturated zone. Hydrodynamic dispersion is described in one dimension for the partially saturated zone and three dimensions for the saturated zone.

TYPICALLY CONSUMES . . .

TYPICALLY PRODUCES. . .