THE OFFSHORE ENVIRONMENTAL IMPACT BY SARNO RIVER IN NAPLES BAY (SOUTH-WEST ITALY)

The Sarno River Basin (South-west Italy) is one of the most polluted river basins in Europe due to widespread industrialization and intensive agriculture. From the geological point of view, it lies between the Somma-Vesuvius volcanic complex and the limestone formations of the Campania-Apennine Chain. The goal of this work has been to establish the influence of the Sarno river on the present sedimentation in the Naples baycontinental shelf by evaluating organic matter contribution and pollution. Sediments samples were collected, by van Veen grab, in 71 stations located offshore the Sarno river between Vesuvian and Sorrento Peninsula coasts. The characteristics of the surface sediments were analysed to highlight spatial trends in the (i) granulometry (grain-size); (ii) total nitrogen, organic carbon and total phosphorus; (iii) metal content (Hg, Cd, Pb, As, Cr,Cu, Ni, Zn, Fe and Mn). The sediment distribution suggested that sediments from the Sarno River prevailed in the central part of the bay between the sand grained deposits from Vesuvius and coarser grained sediments from Sorrento Peninsula. The Sarno River deposition is characterized bysilt/clays rich in organic elements with a high water content. A comparison with a previous study carried out onshore in the Sarno river basin has allowed to interpret the elevated Pb, Zn, Cd, and Hg concentrations most likely related to geological and anthropogenic sources, to underlying volcanic rocks, and contamination from fossil fuel combustion associated with nearby urban centres. In particular, as verified onshore, Ni and Cr contamination is most likely originating from anthropogenic sources as the Solofra tannery industry; the results suggest as these metals have been dispersed offshore. All these elements permit to identify the distribution of the present Sarno prodelta and to identify the influence of the onshore anthropogenic pollution in the adjacent submarine area.First results from this study highlight the influence of the Sarno prodelta in Naples Bay and represent the first step in the characterization of a marine area strongly influenced by a very high populated and touristic coast. Therefore, the study represents a data base for the offshore environmental impact evaluation.