title: Low accessibility and chemical activity of PAHs restrict bioremediation and risk of exposure in a manufactured gas plant soil.
abstract: Composting of manufactured gas plant soil by a commercial enterprise had removed most of its polycyclic aromatic hydrocarbons (PAHs), but concentrations remained above regulatory threshold levels. Several amendments and treatments were first tested to restart the PAH degradation, albeit with little success. The working hypothesis was then that PAHs were "stuck" due to strong sorption to black carbon. Accessibility was measured with cyclodextrin extractions and on average only 4% of the PAHs were accessible. Chemical activity of the PAHs was measured by equilibrium sampling, which confirmed a low exposure level. These results are consistent with strong sorption to black carbon (BC), which constituted 59% of the total organic carbon. Composting failed to remove the PAHs, but it succeeded to minimize PAH accessibility and chemical activity. This adds to accumulating evidence that current regulatory thresholds based on bulk concentrations are questionable and alternative approaches probing actual risk should be considered.
authors.affiliation: Department of Environmental Chemistry and Microbiology, National Environmental Research Institute, Aarhus University, P.O. Box 358, 4000 Roskilde, Denmark.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Reichenberg
authors.forename: Ulrich Gosewinkel
authors.initials: UG
authors.lastname: Karlson
authors.forename: Orjan
authors.initials: O
authors.lastname: Gustafsson
authors.forename: Sara M
authors.initials: SM
authors.lastname: Long
authors.forename: Parmely H
authors.initials: PH
authors.lastname: Pritchard
authors.forename: Philipp
authors.initials: P
authors.lastname: Mayer
mesh_terms: D000327:Adsorption; D052918:Environmental Restoration and Remediation; D007220:Industrial Waste / Q000032:analysis*; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D011084:Polycyclic Aromatic Hydrocarbons; D012989:Soil Pollutants