A 3-Dimensional Model of Density-Dependent Subsurface Flow and Thermal Multispecies-Multicomponent HYDROGEOCHEMical

This report presents a three-dimensional finite-element numerical model designed to simulate chemical transport in subsurface systems with temperature effect taken into account. The three-dimensional model is developed to provide (1) a tool of application, with which one is able to deal with a variety of real-world problems, (2) a tool of education, with which one can study how a factor would affect the whole system, and (3) a substructure, which one could modify to handle specific problems. The hydrological environment to which the model can be applied is a heterogeneous, anisotropic, saturated-unsaturated subsurface medium under either transient-state or steady-state flow conditions. In addition, the temperature within the system of interest can be both time- and location-dependent. For steady-state simulations, strong coupling among subsurface flow, chemical transport, and heat transfer is used in the model. For transient-state simulations, weak coupling is used, but a density effect is still considered in computations. Both the strong and the weak couplings are pictured and explained. The model employs chemical equilibrium to describe the relationship among chemicals. The chemical reactions included in the model are aqueous complexation, multi-site adsorption/desorption, multi-site ion-exchange, precipitation/dissolution, redox, and acid-base reactions. To discretize the domain of interest appropriately, the element used in the model can be a hexahedral, a triangular prism, or a tetrahedral element. To extend its applicability to more real-world problems, two approaches are presented for the chemical transport module in this report. The first approach uses the pore velocity and dispersion coefficient to handle advection and dispersion, respectively, for aqueous comp..

Symposium on hydrogeochemical and stream-sediment reconnaissance for uranium in the United States : March 16 and 17, 1977.

October 1977."GJBX-77(77)"--Cover.Includes bibliographical references.Mode of access: Internet