Application of a Mass Balance-Based Subsurface Contaminant Transport Model

The definition of contaminant source release is a necessary element of contaminant mass transport simulation in the saturated zone. At many sites the release history is unknown, and there has been a significant body of research to develop inverse models to define finite release histories. Instead of rigorously defining the source history, a mass balance-based approach is tested to explicitly account for uncertainty in equal length rectangular pulse release variables. The approach has been incorporated into a spreadsheet model which uses a one-dimensional solution to the advection dispersion equation. A concentration dataset collected at a Superfund site was used for model calibration and verification. Several synthetic datasets with known input parameters were also used for model calibration and verification. The model provided reasonable results when the source time parameters were assumed to be random, and the results improved when the mass of contaminant in the aquifer was also assumed to be random. However, the improvements came at the cost of degraded calibration parameter values.