Multi-Component Simulation of the Transport of Heavy Metals in Groundwater Systems

This paper discusses the development and application of a model that predicts the behavior and transport of heavy metals in the environment. The model, called the Heavy Metal Leaching (HML) model, uses the direct substitution approach (DSA) for simulating oneand threedimensional multi-component solute transport in groundwater and soils. The model has the ability to treat equilibrium reactions of aqueous and surface complexation, precipitation-dissolution, and kinetic diffusion. The concentrations of aqueous component species, adsorbed component species, and precipitated species are selected as the principal dependent variables. The substitution into the transport equation takes place after the transport equation is discretized. The resulting system of equations is solved using the Newton-Raphson method and the Jacobian matrix is computed analytically. This method is computationally more efficient than sequential iteration methods due to its faster convergence rate. It is also more efficient than other direct substitution methods which compute numerically the Jacobian matrix. The HML model was used to simulate 3-D multicomponent behavior and transport of chromium in groundwater and soils. It successfully simulated aqueous complexation, surface complexation, and precipitation and kinetic diffusion reaction processes. The HML model is currently being used as a remedial design tool at sites environmentally impacted by the presence of heavy metals.