Heavy metals in drinking waters from Mount Amiata (Tuscany, Italy). Possible risks from arsenic for public health in the Province of Siena.

Concentrations of As, Al and some heavy metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb) were measured in drinking waters from Siena and Grosseto districts, South Tuscany, Italy. The analysis, performed mostly by electrothermal activated atomic absorption spectroscopy equipped with graphite furnace, and in some cases high-resolution inductively coupled plasma mass spectrometry, indicated that concentrations of the elements were generally far below the maximum allowed concentration (MAC). However, the concentration of As in some of the waters at sources or at the terminals of the water webs was relatively high (largest value, 14.4(2) microg/l) when compared to the MAC(As) value (10 microg/l, December 25, 2003; Italian Law). Relatively high concentrations of some metals had been detected in a few samples from the ends of the distribution webs, when compared to values at sources. These effects are probably due to leaching from metal pipes. A general 'metal index' (MI) for drinking water, which takes into account possible additive effects of N heavy metals on the human health that helps to quickly evaluate the overall quality of drinking waters, is introduced in this paper as MI=?(i=1,N)[C(i)/(MAC)(i)]. Samples from Ermicciolo spring and Siena water web had MI values of 1.1 and 1.3, respectively, showing that the quality of drinking water in town is somewhat worse than that at one of the main sources, at least regarding the 12 elements taken into account.