Differences in PAH desorption and sediment organic matter composition between non-vegetated and recently vegetated...

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.