title: Dissolved organic carbon enhances the mass transfer of hydrophobic organic compounds from nonaqueous phase liquids (NAPLs) into the aqueous phase.
abstract: The hypothesis that dissolved organic carbon (DOC) enhances the mass transfer of hydrophobic organic compounds from nonaqueous phase liquids (NAPLs) into the aqueous phase above that attributable to dissolved molecular diffusion alone was tested. In controlled experiments, mass transfer rates of five NAPL-phase PAHs (log K(OW) 4.15-5.39) into the aqueous phase containing different concentrations of DOC were measured. Mass transfer rates were increased by up to a factor of 4 in the presence of DOC, with the greatest enhancement being observed for more hydrophobic compounds and highest DOC concentrations. These increases could not be explained by dissolved molecular diffusion alone, and point to a parallel DOC-mediated diffusive pathway. The nature of the DOC-mediated diffusion pathway as a function of the DOC concentration and PAH sorption behavior to the DOC was investigated using diffusion-based models. The DOC-enhanced mass transfer of NAPL-phase hydrophobic compounds into the aqueous phase has important implications for their bioremediation as well as bioconcentration and toxicity.
authors: UFZ Helmholtz Centre for Environmental Research, Department of Environmental Microbiology, Leipzig, Germany. kil@dmu.dk
authors: Kilian E C
authors: KE
authors: Smith
authors: Martin
authors: M
authors: Thullner
authors: Lukas Y
authors: LY
authors: Wick
authors: Hauke
authors: H
authors: Harms
mesh_terms: D002244:Carbon / Q000737:chemistry*; D004784:Environmental Monitoring; D008401:Gas Chromatography-Mass Spectrometry; D057927:Hydrophobic and Hydrophilic Interactions; D008962:Models, Theoretical; D009930:Organic Chemicals / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D002244:Carbon