Q-189. Colonization and Remediation of Polycyclic Aromatic Hydrocarbon (PAH) Contaminated River Sediment using Pleurotus ostreatus
Background: Sediment in a 32 mile stretch of the Mahoning River located in northeast Ohio is contaminated with high concentrations of PAHs and metals from the steel industry. The U.S. Army Corps of Engineers is planning a project to restore this stretch of river by dredging. White rot fungi (WRF) produce extracellular ligninases that generate free radicals responsible for lignin degradation and cometabolic degradation of a wide range of organic contaminants including PAHs. The objective of this study is to evaluate potential remediation of PAH contaminated sediment using WRF as an alternative to landfill disposal. P. ostreatus, a WRF, was chosen because it is not a pathogen and prior research shows it aggressively colonizes contaminated soil and can degrade PAHs. PAHs were extracted from triplicate 10 g river sediment samples and analyzed by GC-MS for baseline data. Fourteen PAHs were detected in the range of 1.3 to 27 ug/g sediment ash weight. Fluoranthrene, pyrene, and benzo(a)pyrene had the highest concentrations (27, 22, &18 ug/g respectively). P. ostreatus grown in solid culture (10% by volume) and sawdust (30% by volume) were mixed with river sediment and incubated at 25 oC. Colonization was evaluated by measuring mycelial length (fluorescence microscopy with calcufluor white staining) and by counting WRF colony forming units (WRF-CFU) on selective media (benomyl and streptomycin). After 20 days there were 2.2 + 0.1 X105 WRF-CFU/g. After 23 days there were 900+ 130 microns/g mycelial length. No WRF-CFUs and no fungal mycelia were observed in baseline sediment. After 20 days, triplicate 10 g samples were extracted and analyzed for PAHs as described above. Twelve PAHs decreased to an average of 86% + 6 of their baseline values. Two of the more recalcitrant PAHs dibenz(ah)anthracene and benzo(ghi)perylene showed higher values than baseline (106% and 109% respectively). Sediment heterogeneity likely contributed to these higher than expected values. Drier conditions (less than the observed 31%) would likely improve colonization and PAH degradation. These data indicate that P. ostreatus has the potential to colonize river sediment and that further optimization is required for PAH bioremediation.