Heavy metals backgrounds in sediments from the Sacca di Goro (NE, Italy)

A textural and geochemical characterization of sediments from the Sacca di Goro lagoon floor has been performed in order to evaluate the present day granulometric distribution and the geochemical budget with respect to literature values. 10 samples have been collected along a WE transect crosscutting the whole Sacca di Goro lagoon in order to explore the maximum lithological variability and to identify geochemical trends. Results show that the present day superficial sediment are coarser in grain size with respect to those studied in the past, in turn implying lower concentrations of Potentially Toxic Elements (PTE). PTE enrichments miming those observed 20 years ago are recorded only locally, in connection with parallel increase of fine fraction and organic matter. Traces of Cu, V and Pb have been also found in the shells of farmed Manila clam (Ruditapes Philippinarum) collected within the sediment samples, suggesting PTE bioavailability and accumulation. The comparison of the results with literature data highlights that PTE contents of the Sacca di Goro lagoon deserve more frequent and systematic monitoring both for the high hydrodynamicity of this environment and for the high anthropogenic impact. The analysis of metals in Manila clam shells has a twofold purpose because it represents a further biomarker of the ecosystem, and also provide a geochemical fingerprint of the local shellfish production that could help the traceability in the market, and discrimination from shellfish produced in other area that are not properly controlled from the sanitary point of view.