Mercury and Arsenic Discharge from Circumneutral Waters Associated with the Former Mining Area of Abbadia San Salvatore (Tuscany, Central Italy)

Dissolved and suspended toxic elements in water discharged from abandoned and activemining areas pose several critical issues, since they represent a threat to the environment. In this work,we investigated the water, suspended particulates, and stream sediments of a 2.1 km long creek (Fossodella Chiusa) that is fed by waters draining the galleries of the abandoned Hg mining area of AbbadiaSan Salvatore (Mt. Amiata, Tuscany, central Italy). The geochemical results show evidence that thestudied matrices are characterized by relatively high concentrations of Hg and As, whereas those ofSb are generally close to or below the instrumental detection limit. Independent of the matrices, theconcentration of As decreases from the emergence point to the confluence with the Pagliola creek.In contrast, Hg concentrations display more complex behavior, as water and sediment are mainlycharacterized by concentrations that significantly increase along the water course. According to thegeoaccumulation index (Igeo), sediments belong to Class 6 (extremely contaminated) for Hg. The Igeoof As varies from Class 6, close to the emergence, to Class 2 (moderately contaminated), dropping toClass 0 (uncontaminated) at the confluence with the Pagliola creek. Finally, the total mass load ofHg and As entering the Pagliola creek was computed to be 1.3 and 0.5 kg/year, respectively, when amean flow rate of 40 L/s was considered. The calculated loads are relatively low, but, when the Fossodella Chiusa drainage basin is taken into account, the specific load is comparable to, or even higherthan, those of other mining areas.