Benthic fluxes of mercury in a highly industrialized coastal environment (Mar Piccolo, Taranto, Italy)

Coastal areas of the city of Taranto (Italy), have suffered from intense anthropic and industrial pressures (notably an iron and steel factory, a petroleum refinery, and the Italian Navy shipyard and arsenal) and were declared a “Contaminated site of national interest” in 1998. Previous research showed significant heavy metal contamination of the Mar Piccolo sediments, with higher concentrations in the first inlet where the Navy arsenal is located. High sedimentary Hg contents, in particular, are a cause of concern, given its possible transfer to the aquatic trophic chain and considering the widespread fishing and mussel farming activities in the area. Up to ≈ 8 μg g-1 of total Hg were measured in the Mar Piccolo sediments, while the concentration in seafood was below the limit established by the European Community (0.5 mg/kg w.w.) with the exception of the gastropod Hexaplex t., sampled in proximity of the Navy Arsenal. As Hg is considered a priority pollutant for its toxicity, mobility, and bioaccumulation potential (especially in its organic form methylmercury), a further investigation on the role of sediments as a potential source of Hg to the Mar Piccolo aquatic ecosystem was conducted. The research was carried out in the framework of the “RITMARE - la Ricerca ITaliana per il MARE (2012-2016)” Flagship Project, financed by the Italian Ministry of University and Research (MIUR). The release of Hg from sediments was investigated by means of an in situ benthic chamber, as previously described for other Hg contaminated coastal areas of Italy.