The geochemistry of pore waters in riverbed sediments in a mining-impacted landscape: sources of potentially toxic elements

Geochemical surveys were carried out over three years in the mining area of Alta Versilia. The physico-chemical parameters and the concentrations of potentially toxic elements (PTE) were determined both in mine drainages and in waters of the Baccatoio Stream receiving AMD. AMD have an average pH of 2.2 and contain high concentrations of Al, Fe, Mn, Cu, Zn, As, Ni, Co, Se, Cd, Sb, Pb and Tl. The discharge of AMD into the stream results in a severe contamination. Downstream of the mines, the pH increases and most PTE are readily scavenged from the stream waters by precipitation and adsorption. On the contrary, Tl behaves almost conservatively, undergoing only dilution.