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Small amounts of charcoal in sediments can highly impact the sorption of organic compounds in single solute systems and at low relative concentrations. In the present study, the heterogeneous sorption behavior of charcoals is demonstrated through batch sorption experiments with phenanthrene. The utility of the black carbon content, as measured for soot materials, is evaluated as a measure of the nature of the charcoal material present in sediments. Black carbon content measurements improved predictions of sorptive properties through an additive model but were not sufficient in fully explaining the sorptive behavior observed for the sediments studied in the present work. This is also corroborated through the low and inconsistent measurements of black carbon content observed for laboratory-produced wood chars and natural charcoal samples. Since a quantitative means for prediction of sediment sorptive behavior is not readily available, a more detailed organic petrographical investigation of the charcoals present in sediment samples is pursued. This is a standard method that allows characterization of all (>1–2 μm) organic particles found in a sample. While petrographic methods provide a qualitative description of the sample, it is not possible to use the results to quantitatively predict the overall sorption properties based on this analysis alone. Thus, careful interpretation of qualitative (i.e. microscopy) and quantitative (i.e. black carbon fraction) results should lead us to the determination of a new quantitative property to be used as a predictive tool.