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(80-35) Five-Year Trend of DDT Contamination in Lake Maggiore (N. Italy) using the Zebra Mussel. Binelli, Andrea*,1, Provini, Alfredo1, 1 University of Milan- Dept. of Biology-Via Celoria 26, Milan, Italy ABSTRACT- The mollusc Zebra mussel (Dreissena polymorpha), one of the most used bioindicators of persistent organic pollutants, trace metals and radionuclides in several worldwide freshwater ecosystems, allowed to follow the trend of DDT contamination shown in Lake Maggiore since 1996 and derived from an industrial effluent, located on a tributary of the River Toce, one of the major affluents of the lake. Dreissena specimens were collected at two sampling sites, one inside the Baveno Bay, where the River Toce flows, and the other outside (Villa Taranto). Total DDT levels in the soft tissues of Zebra mussel decreased at both stations by about 30-50% in the first year after the closure of the chemical plant and are now almost in a steady state condition. The high concentrations measured in Zebra mussel specimens of Baveno Bay and the percentage of the parental compound compared to the total DDT concentration, which is similar year by year, clearly indicate that a contamination source is still present, deriving probably from the lacustrine sediments and the River Toce. Data show that the environmental risk is very high within the Baveno Bay and the recovery time should be longer than in the other parts of the lake, where DDT levels in Dreissena are presently two times higher than those measured in other Italian subalpine lakes. Key words: Biomonitoring, Zebra mussel, DDT, Lake |
