IL QUADRO NORMATIVO AMBIENTALE NELLA LAGUNADI VENEZIA. PROPOSTA DI UNA NUOVA PROCEDURA DIGESTIONE DEI SEDIMENTI

A sustainable management of contaminat-ed sediments, in particular in composite and fragileecosystems, needs the updating of the legislation withnew scientific knowledge. This is especially actual inthe Venice lagoon, as has been pointed out in a recentarticle regarding the national and European legislationon dredged sediments administration. Although dur-ing the last few years legislative framework has beenimproved, sediments' management in the Lagoon is ahighly problematic and weighty matter, which stillneeds to be addressed. In this environment recurrentdredging and handling of large amounts of matter, of-ten highly polluted, are indispensable in order to allowthe navigation in the lagoon channels. These opera-tions are regulated by the Protocollo d'Intesa of 1993,which establishes the fate of dredged sediments on thebasis of their total concentration in terms of few or-ganic and inorganic pollutants. As well acknowledgedfor decades by the scientific community, total metalsconcentration don't give indication about their truetoxicity, but rather represents its face value. Moreover,the Venice lagoon is in a continuing state of erosion,loosing huge quantity of fine sediments towards thesea. For these reasons it occurs a deficit of sedimen-tary material required for rehabilitation and mainte-nance of lagoon's morphology and, at the same time,there are large volumes of dredged sediments that, ac-cording to the Protocol, are treated as waste. This iswhy a different legislative approach is necessary, withthe improvement by new scientific knowledge in eval-uating the real risk from contaminated sediments, andtaking due consideration the European legislation inforce. The proposed guideline, product of in-depth sci-entific searches focused in particular on bioavailabil-ity, has been created for lagoon sediment management,but it is relevant also for other environments. Theguideline provides for the application of a TRIAD ap-proach, which consists of an incorporation of chemi-cal, toxicological, and biological data. From the inte-gration of total concentration (of both organic and in-organic pollutants), bioavailable concentration of met-als, and results of toxicity tests, seven different class-es for the sediments are individuated. Each class cor-responds to one distinct degree of risk in dredging thesediment, on the basis of which, different destination,treating or further investigations, are considered. Theapplication of the proposed procedure overcomes thelimitations of local legislation, based on a merely tabular approach. Moreover, the proposed guideline takesinto account the new directives of the legislation inEurope and takes care of human health and environ-mental protection.