Polycyclic aromatic hydrocarbons (PAHs) and petroleum biomarker compounds in sediments of Harrison Reach (Passaic River, New Jersey)

Michael A. Kruge

Dept. of Earth & Environmental Studies and Passaic River Institute, Montclair State University, Montclair, NJ 07043 USA, 973-655-7668 krugem@mail.montclair.edu

As part of the Lower Passaic River Restoration Project, fifteen cores of the top 1.2 m of river bottom sediment were collected on an 80 by 50 m grid in July, 2004, within the Harrison Reach of the Passaic River, downriver from the Diamond Alkali Superfund site at 80 Lister Avenue, Newark, NJ.  The cores were vertically subdivided into quarters and each quarter core was homogenized.  Five of the cores (A3, B3, C2, D2, E1), tracing a 100 m long diagonal across the grid from southwest to northeast, were chosen for organic molecular analysis.  Aliquots of the quarter cores from each of these five cores 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 182 organic compounds were quantitated, including petroleum hydrocarbons (e.g., hopanes, steranes) and detergent marker compounds (linear alkylbenzenes or LABs), as well as parent and alkylated 2 to 6 ring PAHs. The NIST reference standard NY/NJ waterways sediment sample 1944 was also analyzed for comparative purposes.  An environmental forensics approach was taken, that is, relative quantitation results were used to differentiate possible sources of the organic contaminants.  As a guide in the interpretation of the results, principal components analysis (PCA) was employed.

All samples analyzed showed high levels of organic contamination. The isomer distributions within classes of compounds (e.g., dimethylphenanthrenes) tend to show little difference from sample to sample, indicative of similar sources or (post)depositional homogenization. The significant differences occur primarily in the relative proportions of compound classes.  The deeper core segments tend to exhibit similar distributions, with higher relative concentrations of alkylated naphthalenes, phenanthrenes and dibenzothiophenes, as well as isoprenoid alkanes and LABs.  These indicate contamination by petroleum products, coal tar and detergents.  There is more diversity in the distributions seen in the upper core samples.  The PAHs in these samples tend to show a predominance of the parent compounds, implying a relatively greater importance of combustion product input.  There is also a greater proportion of natural organic matter.

While contamination by 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin is of concern in these sediments, PAHs, LABs, and petroleum hydrocarbons are present in concentrations that are up to several orders of magnitude greater.