Chlorinated biphenyls and p,p'-DDE in Mediterranean surface waters

Individual chlorobiphenyls (CBs) and p,p'-DDE were determined in solution and suspension in surface transects of the open Mediterranean Sea in 1987. Large volumes of sea water (1400-1700 dm(3)) were analyzed. Concentrations of CBs were low in solution (<5 pg/dm(3)) and in suspension (<60 pg/dm(3)). Values for their sum (CCB) were 1.7-43.9 and 190-615 pg/dm(3), respectively. Compositions of the CB mixtures in solution as well as those in suspension were very similar in the various transects, but considerable differences were present between solution and suspension in each transect. It was attempted to interpret these differences in terms of molecular characteristics (octanol-water distribution coefficients, K-OW). The resulting plots of log K-OW vs. the apparent distribution coefficient (log K'(d)) gave evidence for the uptake of CBs by suspended particles, followed by sedimentation out of the surface layer. Concentrations in solution were much lower (1-2 orders of magnitude) than those reported before. This may result from improvements in the sampling and analytical techniques. No clear evidence for significant local sources of these compounds was detected in the surface waters, as the levels in solution were very similar to the very low concentrations in the adjacent open Atlantic.