Mercury (Hg) and methylmercury (MeHg) in sediment and biota: A case study in a lagoon in Central Italy

A quantification of total mercury (Hgtot) and methylmercury (MeHg) concentrations in sediment and mussels was carried out in the east basin of the Orbetello lagoon in order to assess their bioaccumulation potential. The sediment was sampled in four macroareas, mussels were transplanted in the same sites and collected after seven weeks. The results show that Hgtot concentrations in sediments exceeded (0.21–16.9 mg/kg dry weight (dw)) the environmental quality standard of the Italian legislation (0.3 mg/kg dw). The Hgtot concentration in mussels (0.050–0.324 mg/kg wet weight (ww)) does not exceed the limit values (0.5 mg/kg ww) of the European food legislation. The biota–sediment accumulation factors (BSAFs) derived for MeHg (80–306.7) and a biomagnification factor (BMF) greater than 1 for Hgtot demonstrate that in the lagoon, these compounds can be transferred in the upper levels of the trophic chain and pose a risk to human health. •The study area is located in the east basin of the Orbetello lagoon in Central Italy.•Mercury and methylmercury concentrations were investigated in sediment and mussels.•Mercury concentrations in sediment exceed the environmental quality standard set by the national legislation.•Bioaccumulation and biomagnification of both mercury and methylmercury have been observed in the lagoon.