PAH sources and depositional history in sediments from the Lower Hudson River Basin

Dated cores and surface sediment samples collected from the Lower Hudson River Basin were analyzed to evaluate the sensitivities and limitations of various polycyclic aromatic hydrocarbons (PAH) source indicators. Results have shown that two molecular ratios, Ring456/TPAH [fraction of PAH with 4, 5 and 6 rings] and Par/(Par+Alkyl) [fraction of PAH with no side chains], are sensitive indicators that may be used to differentiate petrogenic (e.g. petroleum spills) and pyrogenic (e.g. combustion of petroleum, coal, and wood) sources. Specific pyrogenic sources can be identified by isomer ratios of Fl/(Fl+Py) and 1,7/2,6-DMP. Emissions of softwood combustion typically have high ratios (>5) of 1,7/2,6-DMP and Ret/Chy than other sources (<2). U/R ratio [ratio of chromatographically unresolved to chromatographically resolved peaks] is responsive to petroleum usage including petroleum spills and petroleum combustion. The isomer ratios of A/(Pa+A), BaA/(BaA+Chy), and IP/(IP+Bghi) show no correlation with the source-sensitive ratios including delta 13C, possibly reflecting differences in environmental behavior between their constituent compounds and/or less definitive source signatures.; An over 100 year historical record of energy usage in New York City has been reconstructed from the combined application of PAH indicators in one core from Central Park Lake. The reconstructed history is consistent with data provided by the US Department of Energy. Wood combustion was dominant one century ago in Manhattan, followed by coal combustion dominance from the 1900s to the 1940s. Petroleum combustion (mainly motor vehicles in Manhattan) increased gradually from the 1920s, and became the dominant PAH input after 1940s. In most samples collected from elsewhere in the lower Hudson River Basin, petroleum combustion was the dominant PAH input in the last half century. Petroleum spills were considerable sources of PAHs in some harbor samples (e.g. Jamaica Bay and the Passaic River) from the 1960s to the 1980s, and they were the dominant sources in the Arthur Kill during most of the last century. In Newark Bay, coal combustion was a major input in ∼1930, but decreased gradually in the next two decades and remained minor after that. Coal combustion became important in the past several decades in some areas in the mainstem Hudson, presumably due to a major fuel shift from oil to coal in some electricity generating stations along the river. Natural diagenetic sources of PAHs were insignificant in urban waters, but were found to dominate in historical sections of cores from more rural areas of the Hudson Basin.