Accumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans in sediments of the Venice Lagoon and the industrial area of Porto Marghera

Two sediment cores collected from the central Venice Lagoon and five from t he canals of the nearby industrial area were studied in order to assess the temporal evolution of polychlorinated dibenzo p-dioxins (PCDDs) and dibenz ofurans (PCDFs) delivery and present trends. The most polluted site is C12, in the Brentella Canal, with a total equivalent (TEQ) concentration of 285 8 and 64130 ng kg(-1) at the surface and at 18-20 cm depth, respectively. H igh values can be also found in the Nord Industrial Canal and in the Salso Canal: 3000 and 2500 ng kg(-1), respectively. Lagoon samples are much less contaminated, with TEQ downcore maxima of 22 and 53 ng kg(-1), being influe nced by pollutants stored in sediments of the canals only occasionally. Sed iment chronology, based on Pb-210 and Cs-137 activity-depth profiles, shows that the highest fluxes occurred in the 1970s and early 1980s, and that po llution is now decreasing. Homologue profiles can distinguish PCDD/Fs from different sources: combustion for octachlorinated dibenzo p-dioxin (OCDD) a nd stripping of VCM for octachlorinated dibenzofuran (OCDF) alone, whereas several activities carried out in the past within the industrial area can b e responsible of the overall contamination by furans. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.