The correlation of sorption coefficients with nonlinearity of sorption isotherms in contaminated nearshore sediments in Bohai Bay (China)

Phenanthrene sorption to seven nearshore sediments (Bohai Bay, China) collected under similar environments were investigated. Based upon well-fitted Freundlich models, the calculated organic carbon-normalized sorption coefficients at aqueous concentrations of 1 and 5,900 μg/L (PHE supercooled liquid solubility) showed positive and negative correlation with the nonlinearity of sorption isotherms, respectively, and the latter has not previously been reported. The present observations highlighted the viewpoint that PHE at low concentrations is primarily adsorbed to low quantity but highly adsorptive black carbon (BC) whereas partitioning to soft carbon may take over for high concentrations. Therefore, BC should be taken into account when modelling PHE (and analogues) sorption in contaminated sediments, and the correlation approach provides a promising diagnostic tool to this end.