PAH and Saturated Hydrocarbons

Polycyclic aromatic hydrocarbon and saturated hydrocarbon chronologies in sediments deposited from the 1940s to the 1980s have been developed at several sites throughout the Hudson Basin and the New York/New Jersey Harbor complex, including sites 1, 6, 7, 9, and 12 shown on Figure 26.1 (Keane, 1998). The highest levels of PAH were found in Newark Bay (site 12; Fig. 26.1) in samples de-positedin the 1940s and 1950s. Upstreamof the harbor along the main stem of the Hudson, peaklevels of PAH and saturated hydrocarbons were found in samples from the late 1960s and early 1970s. In the more recent samples, the levels were significantly lower. In several cases, saturated hydrocarbon concentrations dropped to less than 10 percent of peak levels. Several Jamaica Bay samples (site 9; Fig. 26.1) had relatively high proportions of lower molecular weight saturated hydrocarbons consistent with inputs of jet fuel from nearby Kennedy International Airport.

Individual PAH compounds in many of the harbor samples have been analyzed for stable carbon isotope ratios. This technique, known as compound specific gas chromatography isotope ratio mass spectrometry (GC/IRMS) provides a powerful tool for PAH source partitioning (O'Malley, Abrajano, and Hellou, 1996). The historical record in Newark Bay cores shows several shifts in the 13 C to12 Cratio that correspond to changes in individual PAH level ratios. Both of these tracers indicate that there have been significant changes in the relative importance of combustion-relatedandpetroleum-derived sources of PAH to Newark Bay sediments over the past sixty years (Perry et al., 2002). Recent work on dated sediment samples has utilized both isotopic and molecular PAH tracers to study temporal and geographic changes in PAH sources to the Lower Hudson Basin (Yan, 2004; Yan et al., 2004).

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