Toxic Modeling in an Industrial Harbor - A Case Study for Baltimore Harbor

Baltimore Harbor, a tributary in the northwest portion of Chesapeake Bay, is historically a major industrial harbor, and has been known for its toxic contaminant pollution from adjacent industries. In order to investigate the fates and the processes of sediment-bound heavy metals in Baltimore Harbor, a three-dimensional hydrodynamic and sediment transport model (CH3D-SED), linked to a toxic model (ICM/TOXI), is applied to the Upper Chesapeake Bay and the sub-domain of Baltimore Harbor. The extended model domain of hydrodynamic and sediment transport, including the entire Upper Chesapeake Bay, provides a significant advantage for investigating interactions between the Harbor and the Upper Bay, while the limited domain for ICM/TOXI (including only Baltimore Harbor) allows more efficient model linkages and computation. A bed sediment sub-model, contained within ICM/TOXI and coupled with the water column model, computes the temporal variation of the sediment concentrations as the result of sediment resuspension, deposition, and physical mixing between different bed layers. Three types of heavy metals, Cr, Pb, and Zn, are simulated in Baltimore Harbor. The model results indicate that with current point source and nonpoint source loadings, the surface sediment contaminant concentration is decreasing gradually. This suggests that the sediment contaminant problem today in Baltimore Harbor is a legacy-related problem. The system is currently in a natural recovery process with regard to the aforementioned three metals. The rate of recovery is a function of current loadings of the concerned materials, the sediment dynamics, and the interaction between the Harbor and the Upper Bay mainstem.