BOX 5-3 Boston Harbor
Chronic contamination of urban harbors reflects a history of contaminant discharges from a variety of sources. Petroleum hydrocarbons, including polycyclic aromatic hydrocarbons, may be derived from the burning of fossil fuels, accidental oil spills, and chronic inputs from municipal discharges and marinas. Loadings of polycyclic aromatic hydrocarbons to Massachusetts Bay are estimated to be within the range of 2.1 to 13.7 metric tons per year (Menzie-Cura & Associates, 1991). Sites receiving inputs from combined sewer overflows (CSOs) are among the most contaminated sites in Boston Harbor and Massachusetts Bays. Concentrations of total PAH in Boston Harbor sediments are among the highest reported for all coastal sites of the U.S. in the NOAA National Status and Trends program. Among sites examined within the New England region, concentrations of total PAH in sediment samples from Boston Harbor exceeded concentrations in samples from other sites by as much as one to two orders of magnitude (MacDonald, 1991). In addition to sediments, biota from Boston Harbor are highly contaminated with a variety of lipophilic organic contaminants including both low molecular weight and high molecular weight PAH. Concentrations of total PAH in tissues of the blue mussel (Mytilus edulis) are in the upper 15 percent of the most contaminated sites from the U.S. coastline surveyed in the National Status and Trends Program (MacDonald, 1991).
The relative abundance of individual PAH in sediments surveyed in Boston Harbor are typical of sediments with highly weathered petroleum inputs mixed with combustion products (McDowell and Shea, 1997). Sediments from Boston Harbor stations are enriched with higher molecular weight PAH indicative of combustion sources and creosote, including fluoranthene, pyrene, and chrysene. McGroddy and Farrington (1995) examined the sediment-porewater partitioning of PAH in three cores from Boston Harbor and found that only a fraction of the total measured sediment PAH concentration was available for equilibrium partitioning and biological uptake. Laboratory desorption experiments demonstrated that only a small fraction of sediment phenanthrene and pyrene were available for equilibrium partitioning (McGroddy et al., 1996). Studies of bioaccumulation of PAH in bivalve mollusks such as the soft-shell clam Mya arenaria and the blue mussel Mytilus edulis also reflect the reduced availability of PAH from Boston Harbor sediments (McDowell et al., 1999). PAH were detected in clam tissues and sediments collected along a gradient of contamination in Boston Harbor and Massachusetts and Cape Cod Bays, but the bioavailability of specific compounds varied at different sites. Estimates of AEP (available for equilibrium partitioning) provided the best predictor of relative bioavailability of pyrogenic PAH.
With the presence of high concentrations of contaminants in Boston Harbor sediments and the need for navigational dredging innovative solutions to dredging Boston Harbor had to be developed. The Boston Harbor Navigation Improvement Project was the result of three decades of negotiation involving many stakeholders and considering 312 land-based inland and coastal sites, 21 landfills, and 21 aquatic sites as disposal options (NRC, 1997). Four final management options were identified as acceptable: the Massachusetts Bay Disposal site, the Boston Lightship site, two near-shore borrow pits, and one contained aquatic disposal site. The final selection involves removal of contaminated sediments to allow dredging of highly contaminated sediments, formation of very deep pits, replacement of the contaminated sediment and, finally, placement of clean sand as a sediment cover. Uncontaminated sediments that are removed to form the deep pits will be disposed at the Massachusetts Bay Disposal site. This solution is a good example of meeting both economic and environmental objectives in the management of contaminated sediments.
Knight Island, Alaska found significantly elevated mortalities of embryos in oiled streams in 1989-1993 (Bue et al., 1998). These findings are indicative of P450 1A induction as measured in oiled streams (Weidmer et al., 1996), as well as with a model of subsurface movement of oil in streams based on intertidal elevations (Rice et al., 2001). These findings were called into question by some subsequent studies on a variety of grounds including questions about study design. Brannon et al. (1995) concluded that oil levels in the redd had no effect on the incubation of fertilized eggs. In a later study, Brannon et al. (2001) claimed that sampling occurred on different time schedules for oiled streams and unoiled streams. Therefore, the authors contended that any damage to eggs was the result of collection and handling, and that oil levels did not negatively impact the embryos. While Rice et al. (2001) clearly showed that their sampling methods had greater power to detect embryo mortality in the field, they were not able to discount the egg-shock hypothesis. However hatchery-raised embryos from parents that were taken from both oiled and unoiled streams had patterns of survival that closely matched those from the field (Bue et al., 1998). Additionally, there was disagreement about damage at other life history stages and laboratory toxicological findings within this species (Brannon and Maki, 1996; Brannon et al., 2001; Rice et al., 2001).
Johnson et al. (2001) reported threshold-sediment PAH concentrations for toxicopathic liver lesions in English sole ranging from 54 to 2,800 ng/g dry weight and a threshold for DNA adducts in liver of 300 ng per g dry weight. These thresholds were based on analyses of fish collected in Puget Sound, Washington. Other effects included inhibited gonadal growth, inhibited spawning, reduced egg viability, and reduced growth, although there were insufficient data to determine a precise threshold. From these analyses, Johnson et al. (2001) proposed a sediment quality guideline of 1000 ppb total PAH (ng/g dry weight) to minimize effects on estuarine