Legacy Contaminant Movement Between River Sediments and Marsh Platform



For decades, PCBs and mercury leached from the waterfront industries of Bergen and Hudson counties, and today, they lie buried in the sediment of the Hackensack River. The U.S. Environmental Protection Agency (EPA) analyzed core samples from the bed of the river between 2016 and 2021 and found high concentrations of contaminants of potential concern, such as mercury and polychlorinated biphenyl (PCBs). Based on this information, in 2022, the Agency added the entire lower Hackensack River to the list of Superfund Sites. Trace elements from the riverbed bind to the fine sediment fraction and are transported by the tides. It is not uncommon for sediment-associated metals to represent > 90% of the metal load in an estuary. Understanding the direction and magnitude of sediment movement under a normal tidal regime allows for better informing and controlling of risks from legacy pollutants. We use 3D velocity meters to characterize the hydrodynamics associated with sediment flows. Additionally, we will use time-integrated "Phillips" samplers to measure fine-grain sediment movement with the tides. We compare sediment mass and associated contaminants moving in and out from six selected sub-basins connected to the river's main stem with different land cover types and surface elevations. We will use the information from this study to inform of the potential risks to vulnerable communities to design management practices and prioritize sites for restoration that help minimize the impact of legacy contaminants on the human population and wildlife in the Lower Hackensack River Estuary.

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