Atmospheric input of organic pollutants to the Venice Lagoon.

The atmospheric deposition of dioxins and furans (PCDD-Fs), dioxin-like polychlorobyphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and hexachlorobenzene (HCB) was determined in the Lagoon of Venice. Sampling was carried out monthly, for a total of 13 months (July 1998-July 1999) using "bulk" samplers (passive collectors of wet and dry depositions) at four sites, inside the lagoon and close to its edge. Calculated PCDD-F loadings to the Lagoon turned out to be quite homogeneous, their range being approximately 10-20 ng m-2 y-1, whereas in the station located close to the industrial zone of Porto Marghera the value was approximately 50 ng m-2 y-1. PCB deposition in the industrial fallout sampling site and in the city centre of Venice was approximately 2500 ng m-2 y-1, that is, almost five times higher than the values measured at the northern and southern lagoon stations. HCB annual loading (approximately 8000 ng m-2 y-1) was almost six times higher in the industrial zone than in the other sites (approximately 1500 ng m-2 y-1). PAH loadings in the city centre of Venice and at Porto Marghera were 314 and 389 micrograms m-2 y-1, respectively. The amount of 2,3,7,8-TCDD equivalents (TEQ) of PCDD-Fs and PCBs in the Venice and Porto Marghera bulk depositions was compared with the guideline value of 15 pg m-2 d-1 for dioxins in depositions proposed by De Fré et al. (1998). Moreover, as some of the effects which drive the risk assessment of dioxin-like compounds were also observed after exposure to other molecules, the TEQs of PAHs and HCB were also calculated: nine out of 13 samples exceeded the guideline value. Lastly, an atmospheric emission source related to vinyl chloride monomer production, which may affect atmospheric deposition on the whole Lagoon, is reported in the industrial zone of Porto Marghera.