DIFFERENCES IN PAH DESORPTION AND SEDIMENT ORGANIC MATTER COMPOSITION BETWEEN NON-VEGETATED AND RECENTLY VEGETATED FUEL-OILED SEDIMENTS

Abstract

We assessed the desorption behavior of pyrene, chrysene, phenanthrene, and tri-alkylated (C₃) phenanthrene/anthracenes for non-vegetated and recently vegetated (< 2 yrs) fuel-oiled sediments collected from the Indiana Harbor Canal (IHC), Gary, IN. Bulk sediment and humin were analyzed for PAH concentrations, organic matter composition, and PAH desorption behavior. PAH desorption isotherms and kinetics were determined using batch aqueous extractions and a two compartment, first-order kinetic model. Vegetated sediments contained more plant carbon and were more nonpolar and less oxidized than non-vegetated sediments. Desorption kinetics indicated that PAH desorption was primarily controlled by a slow PAH-desorbing fraction (F₂) of IHC sediments. However, in vegetated sediments, particularly humin, PAH release from a faster PAH-desorbing fraction (F₁) increased as did the rates (k₂) of PAH desorption from the dominant slow PAH-desorbing fraction (F₂). We propose that vegetation provides aliphatic, nonpolar carbon to IHC sediments that facilitates more rapid PAH desorption from bulk sediment and humin.

KEY WORDS:

• PAH
• sediments
• Phragmites
• desorption
• humin

ACKNOWLEDGMENTS

We thank Pete Lazaro, Thorne Gregory, and John Fountain for their assistance with sample collection and analyses. We appreciate the comments and suggestions of reviewers to improve this manuscript. This work was supported with research funding from The National Science Foundation BES-0337453.

Notes

^aValues are means (n = 3) ± one standard deviation.

^bC₃-phenanthrene/anthracenes

^A denotes mean values that are significantly different [Student t-test (p < 0.05)] between non-vegetated and Phragmites bulk sediments.

^BDenotes mean values that are significantly different [Student t-test (p < 0.05)] between non- vegetated and Phragmites de-ashed humin.

^aValues are means of triplicates ± one standard deviation;

^bValues are means of duplicates ± one standard deviation;

^c Gregory et al., 2008; and

^d% black carbon of total organic carbon; organic carbon after heating (375 C, 24 h).

^ADenotes mean values that are significantly different [Student t-test (p < 0.05)] between non-vegetated and Phragmites bulk sediments.

^BDenotes mean values that are significantly different [Student t-test (p < 0.05)] between non-vegetated and Phragmites de-ashed humin.

^aValues are means (n = 3) ± one standard deviation.

^bC₃-phenanthrene/anthracenes.

^ADenotes mean values that are significantly different [Student t-test (p < 0.05)] between non-vegetated and Phragmites bulk sediments.