Unsaturated Physical Non-equilibrium Contaminant Transport Modeling Using Modified FEMWATER

The unsaturated soil zones beneath the earth surface are vulnerable to several types of harmful and toxic contaminant movements due to various natural and anthropogenic interventions. The convective-dispersive equation, which is traditionally used to describe the contaminant movement in porous media, has drawbacks of prediction in contaminant concentrations that are influenced by physical non-equilibrium that may exist due to presence of mobile and immobile liquids in the void spaces. We attempt in this paper to analyze the influence of physical non-equilibrium in pore water on acid mine drainage (AMD) through unsaturated soils. The United States-Environmental Protection Agency (US-EPA) developed finite-element software FEMWATER, which solves the liquid flow and contaminant specie transport using finite-element methods, is modified to incorporate features of physical non-equilibrium in contaminant transport due to AMD.