Differences in Sediment Organic Matter Composition and PAH Weathering between Non-Vegetated and Recently Vegetated Fuel Oiled Sediments

Abstract

We examined polycyclic aromatic hydrocarbon (PAH) attenuation in contaminated field sediments after only 2 years of plant growth. We collected sediments from vegetated and non-vegetated areas at the Indiana Harbor Canal (IHC), an industrialized area with historic petroleum contamination of soils and sediments. PAH concentrations, PAH weathering indices, and organic matter composition in sediments colonized by Phragmites, cattails, or willow trees were compared to the same indices for non-vegetated sediments. We hypothesized that bulk sediment and humin fractions with measurable increases in plant organic matter content would show measurable changes to PAH attenuation as indicated by more weathered PAH diagnostic ratios or reduced PAH concentrations. Carbon-normalized PAH concentrations were lower in vegetated bulk sediments but higher in vegetated humin fractions relative to non-vegetated sediment fractions. Total organic carbon content was not indicative of more weathered N₃/P₂ ratios or reduced PAH concentrations in vegetated sediment fractions. More weathered N₃/P₂ ratios were observed with increased modern carbon (plant carbon) content of vegetated sediment fractions. Phragmites sediments contained more modern carbon (plant carbon) and more weathered PAH ratios [C₃-naphthalenes and C₂-phenanthrenes (N₃/P₂)] than willow, cattail, and non-vegetated sediments.

KEY WORDS:

• polycyclic aromatic hydrocarbon (PAH)
• ¹⁴C accelerator mass spectrometry (AMS)
• Phragmites
• cattails
• willow trees

ACKNOWLEDGMENTS

The authors would like to thank Pete Lazaro, Carter Reeb, Steve Rock, and Dr. Chris Swanston for their assistance with sample collection and analyses. This work was supported with research funding from The National Science Foundation under grant BES-0337453.

Notes

^a Total alkylated and non-alkylated PAH (TPAH) (n = 42) concentrations of lipid extracts from sediment fractions analyzed at North Carolina State University (NCSU).

^b Mean values of the sum of concentrations of the 16 EPA Priority PAH pollutants in lipid extracts from sediment fractions analyzed at NCSU.

^c Values are mean ± one standard deviation (n = 3).

^A Mean values that are not significantly different (Dunnett's ANOVA, P < 0.05) (Dunnet, 1955, 1964).