Transport mechanisms and fate of polychlorinated biphenyls in the Seine river (France)

The occurrence modalities of polychlorobiphenyls (PCB) in the Seine river at different stations of the Paris area were investigated throughout the year. The progression of the PCB amounts carried by the river was very regular. The annual PCB discharge was similar in the Marne river and in the Seine river before their confluence. The PCBs, appeared to be rather carried in the aqueous phase (63 and 72% at Orly — upstream of Paris and Pont Sully — Paris —, respectively) than in the suspended-sediment (S-Sed). The annual S-Sed flow and PCB flow at Pont Sully were 0.37×106 t and 0.9×103 kg, respectively. The most important amounts of PCBs carried by the river were observed earlier than the flood climax. The PCB and the particulate organic carbon levels in the S-Sed were significantly correlated (P<0.01) at Orly and Pont Sully. Concerning the different PCB congeners, the less chlorinated ones were found in the aqueous phase either during the swelling or during the low-water period.