Hydrogeochemistry in the abandoned mining area of Tafone Graben (Italy): Environmental implications

In Southern Tuscany the Triassic "Calcare Cavernoso" limestone hosts important sulphide deposits. In the Tafone area mineralization consists of stibnite with minor Fe, Cu, Zn, Pb and Hg sulphides. The end of mining works left tailings and waste deposits along the Tafone valley, and two exploited pits are now filled with water. Relatively high amounts of Sb, Zn and As in the tailings were postulated to be the source of a potential contamination in the Tafone hydrological system. A hydrogeochemical study, based on 40 samples, including lake, stream, spring and well waters, was carried out in an area of approximately 130 km2. A survey of chemical characters in waters revealed high salinity of waters with dominant sulphate, and anomalies in Li and B, and contaminants such as Sb and As, in the Tafone stream system. Anomalous concentrations are due to tailings, waste disposal and mining works, but high concentrations of Sb and As in solution have additional sources, such as the interaction processes between waters and the ore-body. The left-hand tributaries to the Tafone stream dilute the concentration of the above species, but Sb and As are available all along the Tafone banks.