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Low accessibility and chemical activity of PAHs restrict bioremediation and risk of exposure in a manufactured gas plant soil |
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| Authors: | Fredrik Reichenberg Örjan Gustafsson Parmely H Pritchard Philipp Mayer |
| Institution: | a Department of Environmental Chemistry and Microbiology, National Environmental Research Institute, Aarhus University, P.O. Box 358, 4000 Roskilde, Denmark b Stockholm University, Department of Applied Environmental Science (ITM), 10691 Stockholm, Sweden c Centre for Ecology and Hydrology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire PE28 2LS, UK d Department of Biology, Portland State University, PO Box 751, Portland, OR 97207, USA |
| 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. |
| Keywords: | Soot Biodegradation Hydrophobic organic pollutants Freely dissolved concentrations Persistence |
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