Impact of Plant Organic Matter on PAH Desorption from Petrogenic-Polluted Sediments
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Date
2007-04-08
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Abstract
Polycyclic aromatic hydrocarbon (PAH) bioavailability does not correlate directly with total PAH sediment concentration because PAHs strongly sorb to organic matter. Many current toxicological models assume that PAHs present in the dissolved phase reflect actual PAH bioavailability to organisms. Plants can release significant amounts of plant organic matter (POM) to soils and sediments; however, the mechanisms by which POM may affect PAH bioavailability in sediments are unclear. The rhizosphere may increase PAH bioavailability by destabilizing soil organic matter (SOM) and enhancing PAH desorption, or the rhizosphere may alter SOM composition and provide new carbon matrices to sorb⁄sequester PAHs and reduce PAH desorption. Desorption studies were conducted to determine if vegetation decreased or increased the rate and mass amounts of desorbable PAHs. Replicate desorption studies were conducted using vegetated and non-vegetated bulk sediment and HF⁄HCl humin fractions; sediments were collected from a coastal refinery distillate waste pit (RP) and refinery-impacted sediments from a freshwater canal (IH). Desorption isotherms for four PAHs were determined by two methods, aqueous and TenaxTM bead extractions. PAHs were quantified by gas chromatography⁄mass spectrometry selected ion monitoring (GC⁄MS SIM). Results showed differences in PAH desorption based on the amount of time vegetation had been present in sediments. Vegetated sediments with 30+ years of vegetative growth (RP) desorbed more PAHs than non-vegetated sediments by TenaxTM extraction in both bulk and humin sediment fractions. Recently vegetated, IH freshwater sediments desorbed fewer PAHs than non-vegetated IH sediments by aqueous and TenaxTM extractions in bulk and humin sediment fractions. These findings suggest that initial exposure of sediment to vegetation slows PAH desorption and that extensive exposure to vegetation enhances PAH desorption from both labile and refractory SOM.
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bioavailability, Phragmites australis, desorption, PAHs
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Degree
MS
Discipline
Natural Resources
