The development of models of contaminant migration via bioturbation is the focus of this work. Two models are developed from two types of organism activity: organisms that mix sediment vertically (e.g., by burrowing) and those that mix sediment horizontally by movement confined to a given depth below the sediment-water interface. The models are compared to experimental measurements with deposit-feeding oligochaetes that are of the burrowing type. Both models provide a good description of the contaminant flux and average concentration profile. It is not possible to differentiate between the models on the basis of the available data.