Vertical flux and particulate/water dynamics of polychlorinated biphenyls (PCBs) in the open Baltic Sea

Concentrations of PCBs in water (dissolved), suspended particles (SPM), sed iment trap material, and sediments in the Baltic Sea are discussed in relat ion to the dynamics of organic carbon and lipids as the sorbing matrices. B oth carbon- and lipid-normalized concentrations of PCBs in SPM increase dur ing the sedimentation giving rise to an increase in observed log K-oc with more that one order of magnitude for most of the studied PCBs. It appears t hat hydrophobic organic compounds (HOCs) are retained within the settling p articles while the organic carbon and the lipids are degraded, rather than there being a continuous uptake of PCBs during settling. However, the expla nation for the high concentration maintained in the sediments over long tim e periods, must be an increasing capability of the organic matrix to sorb H OCs during the ageing process. The results are of importance for current mo dels of the fate of HOCs in the environment and imply that the use of a sin gle equation to estimate equilibrium concentrations of HOCs in SPM may sign ificantly underestimate concentrations in settling particles.