Fate and Transport Modeling of Sediment Contaminants in the New York/New Jersey Harbor Estuary

摘要

Sediment contamination in the New York/New Jersey Harbor estuary has adversely impacted both the disposal costs and the disposal options for material dredged from the Harbor. In response to this problem, the Port Authority of New York and New Jersey and several state agencies, through a bi-state dredging agreement, formed the Contamination Assessment and Reduction Program (CARP). One aspect of CARP was the development of a series of numerical models that serve as both diagnostic and predictive tools. The CARP numerical models include hydrodynamic, sediment transport, organic carbon production, contaminant fate and transport, and bioaccumulation models. These models account for the causal link between external sources of contaminants, such as tributary headwaters, sewage treatment plants, urban runoff, combined sewer overflow, atmospheric deposition, and landfill leachate, to ambient concentrations of multiple contaminant classes in water, sediment, and biota of the Harbor. The contaminant classes considered include PCBs, dioxin/furans with 2,3,7,8 substitutions, organochlorine pesticides related to DDT and chlordane, PAHs, and the metals cadmium, mercury, and methyl mercury. After several years of development and calibration, the CARP models now diagnose how much of observed Harbor contamination results from current loadings versus legacy contamination still remaining in the system. Further, the CARP models have been used to forecast expected future contamination levels achievable through natural attenuation and a combination of natural attenuation and various reductions of current loadings and/or removal and remediation of in-place sediments. The modeling approach and application applied under CARP serves as an excellent case study for other urban estuaries and ports. Although developed specifically for the New York/New Jersey Harbor, the CARP model kinetic formulations are easily transferable to other systems. Some of the novel features of the CARP model include mechanistic mercury methylation kinetics and the inclusion of a eutrophication model.