Preferential Sorption of Planar Contaminants in Sediments from Lake Ketelmeer, The Netherlands

Abstract

Organic carbon normalized sediment-water distribution coefficients ( K OC ) of a series of in situ and (mass-labeled) added chlorobenzenes, PCBs, and PAHs were determined in an aged and a more recently deposited sediment layer from Lake Ketelmeer, The Netherlands, using the cosolvent method. The resulting log K OC 's for both in situ and added compounds are rather high compared to literature data (up to 9.3 for benzo[ ghi ]perylene), with the ones in the recently deposited layer being generally higher than those in the aged layer (up to 1.6 log units). The results do not show the well-established effects due to increased contact time of contaminants with sediments (i.e. “aging” or “slow sorption”) and indicate that after only short equilibrium times (11 days) K OC 's can even be higher than after several decades of contact time in the field. In addition, distribution coefficients show a remarkable dependence on sorbate planarity, manifested by significantly different log K OC −log K OW relationships for planar (chlorobenzenes, PAHs, and mono- ortho -substituted PCBs) and nonplanar (multiple- ortho -substituted PCBs) contaminants in both sediment layers. The confirmed presence of sootlike material for which planar aromatic compounds probably have strong affinity is brought up to explain these observations. Differences in K OC 's between both layers are discussed in relation to contact time and analyzed soot fractions.