Historical sediment record and distribution of polychlorinated biphenyls (PCBs) in sediments from the Adriatic Sea (Italy)

EU FP7 Project (Policy-oriented marine Environmental research in the Southern European Seas) aims to identify the interacting patterns of natural and human-derived pressures on the Mediterranean and Black Seas, to assess their impact on marine ecosystems in the framework of the Marine Strategy Framework Directive (MSFD. In the context of the ‘ADREX: Adriatic and Ionian Seas Experiment’ within the PERSEUS project, a monitoring survey has been conducted in order to investigate spatial and temporal patterns of polychlorinated biphenyls (PCBs) in sediments from the Adriatic Sea (Italy). To this end, surface sediment along transversal-to-the-coast transects and undisturbed sediment cores were collected at four coastal areas: the prodelta Po River, Ancona, Gargano Promontory and Bari. The spatial distribution of total PCB concentrations in surface sediments varied between 4.1 μg kg-1 and 0.84 μg kg-1, and revealed a decreasing pattern from the northern to the southern Adriatic Sea. The maximum concentration of total PCBs was detected in the Po River Prodelta area, and the lowest concentrations in the Bari coastal area. The historical trends of PCBs showed a common pattern, with increasing concentrations from the lower horizons to the middle sections of sediment cores, followed by a decreasing trend upwards in the surface layers deposited in recent years. Historical data on PCBs show that production and emissions increased sharply from the mid 1960’s to 1980’s in Italy; the trend reversed at the end of 1980s continuing to decrease in the following decades. Concentrations found in middle sections of sediment cores probably recorded periods of higher production and emission of PCBs, while the lower concentrations found in the upper layers most likely reflected ban/restriction on PCB production and use in Italy due to incoming European regulations. Despite the low levels of total PCBs found in surface and middle sections of sediments when compared to highly urbanized coastal areas in the World, concentrations have declined with distance from the Po River Prodelta southward, suggesting the Po River outflow to be a major contributor of PCBs to sediments in the Adriatic Sea. In addition, the presence of PCBs in areas far from the direct source of input and the congeners pattern suggest that PCBs in the sediments from the Adriatic Sea may also come from discharges of local sources, as well as atmospheric deposition.