Sorption of polychlorinated biphenyls by North Sea sediments

The sediment-water partition coefficients (K-d) of 32 polychlorinated biphenyls (PCBs) and penta- and hexachloro benzene were determined for 37 spiked sediment samples from the southern North Sea, the German Eight and the Norwegian Channel. Organic-carbon contents for these sediments were in the range 0.02-2.4%. Log(K-d) values were in the range 1.4 to 5.3. The largest difference between the organic-carbon normalised partition coefficients (K-oc) for individual components amounted to a factor of 10. K-oc values for coarse sediments were generally lower than values for fine sediments. The solids concentration effect was evaluated using the Non-Settling Particles model, the Solute Complexation model, the Implicit Adsorbate model, and the Particle Interaction model. The latter three models could be rejected on the basis of the experimental evidence. The validity of ordinary least-squares regression for estimating slope and intercept of log(K-oc)-log(K-ow) relations is discussed. Differences in sediment characteristics cause changes in the intercept of log(K-oc)-log(K-ow) relations, but not in the slope. K-oc values of PCB isomers are inversely related to the number of chlorine atoms in the ortho position relative to the inter-ring bond. The validity of the data for estimating field values of sorption coefficients is discussed.