Assessment of Mercury Contamination in Surficial Sediments of Newark Bay

EXECUTIVE SUMMARY This study of mercury contamination in Newark Bay sediments was initiated from a broader study of mercury sources and material balance in the New York-New Jersey Harbor, conducted for the New York Academy of Sciences' Harbor Consortium by Themelis and Gregory (2001). The author of this report concluded that a more in-depth study should be conducted on a smaller area within the Harbor where mercury contamination has been historically significant. This conclusion was also based on results from a recent study by Gregory and Gorokovich (200 I), where geographic information systems (GIS) technology was used to visualize the high Hg concentrations in Newark Bay surficial sediments from 1988 to 2000. As a result, it was determined that this study should include a discussion of a) health risks associated with mercury exposure originating in aquatic environments, b) sediment and water quality characteristics that influence mercury methylation, c) source of Hg contamination to Newark Bay, and d) assessment of mercury contamination of Newark Bay sediments. Newark Bay was chosen as the study area because it has historically contained some of the most anthropogenically enriched Hg sediments compared to the rest of the NYINJ Harbor. Furthermore, most Hg-related industries in the Hudson-Raritan (HRB) were historically concentrated within the Newark Bay vicinity. Municipal wastewater treatment plants (WWTP) were the next largest point source contributors of mercury to Newark Bay. Tributary flow from the Hackensack and Passaic Rivers and tidal flow from the Arthur Kill and Kill Van Kull transported these plant effluent discharges into Newark Bay. However, NJ DEP reported significant reductions in WWTP emissions between 1987 and 1998. These reductions are most likely attributed to the phasing out of mercury in industrial applications, and possibly improved Hg recovery techniques by enzymatic reduction of soluble divalent mercury (Hg 2) to insoluble elemental mercury (Hg o) by mercury resistant bacteria. The sediment analysis using geographic information systems (GIS) demonstrated that Newark Bay surficial sediments had high mercury concentrations relative to the rest of the Harbor over a twelve-year period (1988-2000). This method of analysis was useful in identifying sites of potentially high methyl Hg production based on the presentation of Hg and total organic carbon data in Newark Bay. However, it was not capable of modeling Hg methylation given the data deficiencies and technical limitations. Surficial sediments were chosen as the medium of analysis because the most intense biogeochemical activity occurs at the …