Polycyclic aromatic hydrocarbons in sediments of the Venice Lagoon

Three sediment cores were collected in the Venice Lagoon: two from mud flats (E, F) and one from the San Giuliano Canal (I1), which borders the industrial district. Samples were analysed for the 15 polycyclic aromatic hydrocarbons (PAHs) listed as priority pollutants by the U.S. EPA. Sediment chronologies were established using both 137Cs and 210Pb activity-depth profiles, and confirmed by independent information. The highest levels of PAHs, up to 16,474 µg kg-1, characterise the sediment from the industrial canal. In lagoon sediments maximums were 618–1,531 µg kg-1, while surficial values were 315 and 810 µg kg-1. Dated concentration-depth profiles suggest that highest inputs occurred in the first half of last century and were followed by significant decreases. The industrial activities played a major role in the PAH contamination of lagoon sediments, as suggested by the high concentration gradients in the study area. The main source, based on the information provided by the relative abundance of congeners, is represented by high temperature combustion processes. Petrogenic sources may have influenced some samples, whereas the effects of selective transport and diagenesis are difficult to assess. The sediment of the industrial canal has the potential to occasionally cause adverse effects in sensitive species.