Thallium contamination in waters from an Alta Versilia (Tuscany, Italy) catchment: from environmental impact of past-mining activities to human health threats

Introduction. The mining activity. after decommissioning, may generate environmental impacts by acid drainages (AMD) and the release of toxic compounds to the ecosystem. Although acidity in mine drainages has been receiving most of the attention, the primary sources of toxicity for the biota and humans are the dissolved toxic and potentially toxic trace metals (PTE). PTE can reach elevated levels of concentration not only in acidic but also in pH-buffered waters; in fact, the pH and alkalinity increase that may occur in mine eflluents by the buffering reactions does not necessarily prevent metal transport and dispersion by the aqueous phase throughout the ecosystem. Actually, some elements such as Fe, Al and Cu are readily scavenged from the aqueous phase at increasing pH by adsorption on solid surfaces and/or co-precipitation reactions becoming confined into sediments. On the other hand, ionic species of elements such as thallium (Tl) with a low affinity for suspended partclesundergo little removal reaching concentrations of hundred of ug/L in waters draining the mineralized areas. IN Particular, Tl is hosted within base metal sulfides such as chalcopyrite, pyrite, galena and sphalerite event at wt% amounts, besides forming rare Tl sulfosalts and secondary sulfate minerals, and may be readily mobilized to waters during weathering and transported through the aquoeus routes...... The present study reports the first results of a survey on waters from the Baccatoio Torrent catchment, in Alta Versilia (Apuan Alps, Tuscany, Italy), showing estremely high concentrations of thallium in acid mine drainages anc concentration of concenr in some springs with implications on dispersion in the environment and pollution of the drinkable water system of Valdicastello Carducci village and Pietrasanta town....