The PCB's in the marine environment. Geochemical aspects of inputs and distribution. A case studied: the french shoreline
PCB's are a group of chlorinated chemicals particularly persistent in the environment. The total global production of PCB compounds is evaluated at 1 200 000 tons and about 30 % are dispersed in the environment, mainly in the oceans. Distribution of these substances in the aquatic environment depends on exchange mechanisms at seawater/atmosphere and seawater/sediment interfaces, at abiotic and biotic transformation processes and at bioconcentration processes in the biota. Twenty years of research work allow us to describe with sufficient precision the biogeochemical cycle of PCB's in the marine environment. The PCB contamination of the French coastal marine environment is investigated more closely. Total PCB production in France is evaluated at 123 000 tons and pollutant inputs to the coastal marine environment, via rivers and atmosphere, are estimated between 2.5 and 3.0 tons/years. The Least polluted zones are in the English Channel along the north coast of Brittany till Normandy (West Cotentin) and in the Mediterranean along the east coast of Corsica. The most highly polluted area is constituted by the estuary and the bay of the Seine which receive river pollutant inputs. High PCB contaminations are also observed in industrial and urban zones, and in areas which receive untreated urban sewage (ex. Marseille). Several short-term surveys let us suppose there has been a general decrease in PCB levels along the French coastal marine environment in the last decade.