Cation exchange in groundwater solute transport

The transport and fate of pollutants in groundwater is an important environmental concern. Adsorption processes, such as cation exchange, affect the movement of many contaminants. Accurate modeling of these processes is necessary for the design of efficient aquifer restoration methods. That accuracy depends on both the mathematical description of the transport process and the quantification of the effective adsorption parameters. The objectives of this study were: (1) to formulate a procedure for estimating effective aquifer adsorption parameters in situ, and (2) to test the procedure in controlled laboratory experiments. The parameter estimation procedure used a groundwater contaminant transport model combined with a nonlinear parameter estimation technique. Two- and three-component cation exchange experiments were performed in a two-dimensional injection-production flow apparatus. The parameter estimation procedure computed effective exchange parameters that were consistent for all of the experiments.