Mine wastes at the polymetallic deposit of Fenice Capanne (southern Tuscany, Italy). Mineralogy, geochemistry, and environmental impact

The polymetallic (Zn, Cu, Pb, Fe, Ag) sulfide deposit of Fenice Capanne, southern Tuscany (Italy), was mined at least 6-7th centuries B.C. until 1985, Mine wastes include dumps of roasting products and excavation wastes, mainly dating back to the 19th century, and flotation tailings produced during the period 1950-1984. The mine wastes show significant contents of polluting elements [maximum values (mg/kg) in flotation tailings and roastings As: 1,100; Cu: 7,500; Pb:10,100; Zn: 13,600]. Tailing piles show more intense leaching and acidification compared with later basin filling tailings. The greater effective porosity, as a result of coarser grain size, and the unsaturated conditions that occur in the tailing piles have enhanced sulfide weathering, compared with the fine grained and nearly saturated flotation material present in the settling basins. However, flotation tailing samples show overall negative values of net neutralization potential (NNP), as determined by a standard Sobek test. This emphasizes the importance of maintaining the present hydraulic conditions within the basins to prevent the generation of acid drainage in future. The alteration of mine waste materials have produced pollution in surficial waters and sediments. The pollutant transport in surficial waters occurs mainly as suspended fine-grained sediments containing traces of heavy metals. A possible remediation plan could include building a settling pond for drainage waters, and moving the polluted sediments and unconfined tailing materials into the basins.