Modeling Solute Transport in Ground Water At or Near Freezing

Abstract

AbstractUnder freezing or near‐freezing conditions, temperature‐induced viscosity changes, solute immobilization, and solute exclusion can affect field‐scale solute transport in ground water. This can lead to concentration profiles significantly different from those predicted by models which do not account for these processes. A model (GWFREEZE) is presented which incorporates these processes into a two‐dimensional transport equation for saturated porous media subject to a hydraulic head field that does not vary with time.Ground‐water temperature can be expected to vary widely in some natural and artificial freezing and near‐freezing situations. Spatially varying temperature fields cause spatial variations in the fluid viscosity field, especially near 0° C, where viscosity varies faster with temperature than at higher temperatures. GWFREEZE models these phenomena with a viscosity‐dependent hydraulic conductivity that is a function of temperature. Solute exclusion is modeled by a variable exclusion coefficient (Ke) which represents the percentage of solute excluded at the freezing front. The freezing front is modeled as a planar no‐flow boundary behind which solutes are immobilized and at which solutes are excluded.