Mercury diffusion and distribution in the Hg mining district of Monte Amiata (Southern Tuscany, Italy)

In aquatic environment, mercury (Hg) is taken up by biota such as fish, in the organic form of methyl-mercury (MeHg) and may become available to humans. This study focuses on the distribution and transport of Hg in the Paglia River ecosystem, located downstream from the abandoned Abbadia San Salvatore mine (ASSM). The ASSM is part of the Monte Amiata district (Southern Tuscany, Italy), one of the world’s largest Hg districts. Total Hg (THg) and MeHg were determined in stream sediment and mine waste calcine samples collected from the Paglia River ecosystem. Downstream transport of Hg from mined areas is the dominant source of Hg to this ecosystem. Two fish species, roach (Chondrostoma genei) and barbel (Barbus plebejus), were also collected from the Paglia River and analysed for THg in order to evaluate transference of Hg to biota. Data indicate that THg concentrations of stream sediment samples collected downstream the Abbadia mine are high, often exceeding the probable effect concentration (PEC) for Hg of 1.06 μg/g. Calcine samples contain THg concentrations as high as 1,500 μg/g. Elevated concentrations of MeHg in mine waste calcine and stream sediment samples indicate active methylation of Hg. Concentrations of Hg in fish are high, although additional data are needed to fully understand its distribution in biota of the Paglia River ecosystem.