Combined application of delta C-13 and molecular ratios in sediment cores for PAH source apportionment in the New York/New Jersey harbor complex

Sub-basins within the New York/New Jersey (NY/NJ) Harbor host variable amounts and sources of polycyclic aromatic hydrocarbons (PAHs). Analyses of radionuclides Cs-137 and 7 Be were used to assign approximate dates to individual sections of sediment cores collected from four major sub-basins of the harbor complex. Sampling sites range from heavily contaminated Newark Bay and Passaic River to less contaminated Raritan Bay and Jamaica Bay. PAHs were identified with GC-MS and quantified by GC respectively. Gas chromatography-isotope ratio mass spectrometry (GC/IRMS) was applied to determine delta C-13 values of pyrene (delta C-13(Py)), a principal 4 ring parent PAH. Two end-member PAH source components, petroleum-related PAHs (PRPAH) and combustion-related PAHs (CRPAH), were calculated from a carbon isotopic mass balance equation based on assumptions that petroleum-related delta C-13(Py) is -29 parts per thousand, and that combustion-derived delta C-13(Py) is -24 parts per thousand. Temporal trends of PRPAH in these cores are similar to those of the petroleum-derived unresolved complex mixture (UCM), whereas CRPAH resembled trends of "Total" PAH (TPAH). Three molecular ratios, fluoranthene to fluoranthene plus pyrene (F1/(F1 + Py)), high molecular weight 4-6 ring PAH to total PAH (Ring456/TPAH) and parent to total (Par/(Par + Alkyl)), correlate strongly with each other, and show a moderate to strong positive correlation with delta C-13(Py). In contrast, the ratios of anthracene to phenanthrene plus anthracene (A/(Pa + A)), benzo[a]anthracene to benzo[a]anthracene plus chrysene (BaA/(BaA + Chy)), and indeno[1,2,3-cd]pyrene to indeno[1,2,3-cd]pyrene plus benzo[ghi]peryiene (IP/(IP + Bghi)) show no, weak, or even negative correlation with the four well correlated ratios (delta C-13(Py) Par/(Par + Alkyl), F1/(F1 + Py), and Ring456/TPAH). Combined application of the four well correlated molecular indicators suggests that PAH contribution from combustion became more important in most areas of the NY/NJ Harbor during the last three decades of the 20th century. (c) 2006 Elsevier Ltd. All rights reserved.