Characterization and assessment of contaminated sediments in Lower Passaic River, New Jersey

The Passaic River System is located within the New York-New Jersey Harbor Estuary. A wide range of toxic chemicals, including heavy metals, pesticides, polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) have been found in both sediments and water of the Passaic River.; This research provides a holistic characterization and assessment of pertinent chemicals of concerns through the analysis of the existing 10 years (1991-2000) contaminant data from the lower Passaic River. This work provides novel integrated evidence on the fate and transport of contaminated sediments in the river that will be beneficial to better environmental management.; In this study, radionuclide tracers (210Pb and 137Cs) were used to estimate the sediment deposition rates in the lower Passaic River and found that the average sedimentation rate is 4.1+/-0.5 cm y-1 with a fairly good agreement between these two radionuclides (r2 = 0.89, n = 29). Estimated sedimentation rate from natural radionuclide 210Pb profiles were 4.6 cm y -1 for the study area, providing steady-state sedimentation, while anthropogenic 137Cs gives a 32-years (1963-1995) average sedimentation rate of 3.6 cm y-1. It was found that the sedimentation rates in the lower Passaic River varied from <1 to 13 cm y-1 based on 210Pb and 137Cs profile, which is consistent with that in nearby Hudson River estuary and Newark Bay. A wide range of variations in sedimentation rates estimated from 210Pb profile and 137Cs profiles indicate high spatial variations in sedimentation rates in the lower Passaic River, implying that physical disturbances such as hydrodynamics play a significant role in the system. Some of the 210Pb profiles exhibit non-steady-state sediment deposition, supporting the hypothesis that the bed is physically reworked and short-term deposition is episodic.; During this study, Geographic Information Systems (GIS) were applied to characterize contaminant fate and transport of selected heavy metals (Cd, Cr, Pb, Hg, Ni and Zn) in the lower Passaic River. Results show that the average concentrations of some selected metal contaminants exceed their respective sediment criteria defined by federal or state agencies. The analyses of contaminant concentrations in upper layer sediments (<15 cm) reveal that most "hot spots" with elevated metal concentrations are within the Harrison Reach of the River. Contamination assessment based on the contaminant inventories reveals that Harrison Reach is the most abundant area harboring contaminants in terms of mass per unit area within the lower Passaic River. The concentrations of selected contaminants (e.g., Cr, Pb, Hg, Ni, and Zn, TCDDs and total DDTs) of concern were compared with different sediment quality benchmark, below which adverse effects are unlikely, to determine the hazard quotients (HQ). It was found that the contribution of TCDDs to the potential toxic risk in the Passaic River was over 99% in all the years and average concentrations ranging from 0.007 to 0.02 mug g-1. For all the metals, Pb and Hg poses the highest risk, with HQ > 268 for Pb and HQ > 58 for Hg based on the sample analysis from the 1995 sampling. The degree and spatial extents of contaminant "hot spots" in this research related well with proximity to anthropogenic sources, suggesting localized point source inputs. In this study, Harrison Reach is identified as the river segments posing the greatest potential risk for all chemicals analyzed while TCDDs and Hg are identified as the primary drivers of potential risk in all reaches along the lower Passaic River. Although a variety of chemicals of concern contaminates the Passaic River, there is a good spatial relation of TCDDs concentrations to the concentrations of other chemical contaminants. In other words, most TCDDs localized hot spots are also hot spots for other contaminants of concern. Therefore, remediation of TCDDs could address the...