Significance of Polycyclic Aromatic Hydrocarbons (PAHs) and Petroleum Biomarker Compounds in Contaminated Passaic River Sediments

The lower Passaic River (northeastern New Jersey) flows through one of the most densely populated regions of the United States. The area’s long history of industrial activity is reflected in the complex and variable hydrocarbon composition of the river sediments. Sediments from river bottom grab samples at Newark and a 30 cm deep core at Kearny were subjected to thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS). This technique offers a practical alternative for rapid, inexpensive analysis, simply employing milligram quantities of dry, disaggregated sediment, avoiding the use of hazardous organic solvents. For each sample, a total of 181 hydrocarbons and organosulfur compounds were quantitated, including normal and isoprenoid alkanes, tricyclic terpanes, hopanes, steranes, sterenes, linear alkylbenzenes, C0-C4 alkylnaphthalenes, C0-C3 alkylphenanthrenes and anthracenes, C0-C2 alkylpyrenes and isomers, C0-C2 alkylchrysenes and isomers, 5 and 6 ring parent PAHs, C0-C2 alkyldibenzothiophenes, and C20 isoprenoid thiophenes. As a guide in the interpretation of the results, principal components analysis (PCA) was employed. The resulting first two principal components accounted for 65% of the variance in the data set. While all samples appear enriched in PAHs and petroleum biomarkers, there are considerable differences in the distributions of these compounds from sample to sample. PCA results delineate three distinct chemostratigraphic zones in the Kearny core, each approximately 10 cm thick. The lower zone is enriched in alkylated three and four ring PAHs and dibenzothiophenes, as well as five ring parent PAHs and isoprenoid thiophenes, relative to rest of the core. The middle zone shows relative enrichment in isoprenoid and normal C14-C24 alkanes, alkylnaphthalenes, and dibenzothiophenes. The upper zone exhibits relative enrichment in C25-C31 n-alkanes, sterenes, linear alkylbenzenes, parent PAHs and isoprenoid thiophenes. The Newark surface grab samples resemble the upper Kearny core samples, although they show relatively higher concentrations of hopanes, steranes, linear alkylbenzenes, and isoprenoid thiophenes. The PCA results indicate distinct differences between the grab samples themselves, but of lesser magnitude than those observed within the core