An assessment of sediment contamination in Presque Isle Bay, PA, with historical comparisons

Abstract

The harbor at Erie, Pennsylvania, known as Presque Isle Bay (the 43rd Great Lakes Area of Concern), has been designated by the United States Environmental Protection Agency as being in a stage of recovery. The impaired beneficial uses include the high incidence of fish tumors and restrictions on dredging. The goal of this study was to assess the level of chemical contamination in Bay sediments, and to some extent its tributaries, and to compare the findings to prior studies. Parameters investigated were the previously identified contaminants of concern: selected heavy metals and polycyclic aromatic hydrocarbons. The acid volatile sulfide/simultaneously extracted metals ratio was used to estimate bioavailability of metals. It appeared that the deepest sediments and the most recent sediments were less contaminated with heavy metals and polycyclic aromatic hydrocarbons than those sediments in the middle region studied, that is, from about 10 cm below the surface to about 30 cm below the surface. These more highly contaminated sediments are estimated to represent deposition during the second half of the 20th century. The most recent results for the most superficial sediments are encouraging for stakeholders because there were fewer cases of heavy metals exceeding their respective probable effects concentrations. The metals of greatest concern continued to be Cd, Ni and Pb, in that order. The sites most contaminated with heavy metals were those off Cascade Creek and the site least contaminated with heavy metals was the one nearest the mouth of Mill Creek. Data on stream sediments suggest that more work must be done within the watershed, especially the Cascade Creek and Myrtle Street drainages, to reduce the level of metal contamination reaching the Bay via sediment particles. In the most recently studied sediments certain metals continued to exist at levels approaching or exceeding their probable effects concentrations. However, the acid volatile sulfide/simultaneously extracted metals hypothesis suggests that those metals are not bioavailable. The pattern of polycyclic aromatic hydrocarbon contamination is similar to that of the metals, with the most highly contaminated sites being those along the city's waterfront and in the center of the Bay. The hydrocarbons measured in the most recent sediments were all lower than those measured in 1994, and were well below the probable effects concentration for total polycyclic aromatic hydrocarbons. While there may be other important factors not studied or reviewed in this paper, these findings suggest that heavy metals and polycyclic aromatic hydrocarbons, as of 2003, likely exert only a moderate adverse impact on the aquatic ecosystem of Presque Isle Bay.