Major and trace elements in tap water from Italy.

Tap water is a fundamental resource for everyday life, it is subjected to several routine controls and needs to fulfill many compliance scheme. Several elements are monitored on a regular basis, but many trace chemical elements are not usually analyzed, so there is the need to have some kind of indication about their concentration and variation ranges in order to better assess the water quality. An opportunity for such investigations has been provided by a project of the EuroGeoSurvey Geochemistry Expert Group aimed at the characterization of groundwater geochemistry using bottled mineral waters purchased in supermarkets all over Europe which included also the analysis for comparative purpose, of tap water. The initial tap water database of 24 sites has been subsequently increased to the final number of 157 distributed all over Italy and representative of end-user situations (either private houses and public places). In the samples, pH, conductivity and concentrations of 69 elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Sm, Sn, Sr, Ta, Tb, Te, Th, Ti, Tl, Tm, U, V, W, Y, Yb, Zn, Zr, Br -, HCO 3 -, Cl -, F -, NH 4 +, NO 2 -, NO 3 -, PO 4 3-, SO 4 2-,SiO 2) were measured at the BGR geochemical laboratories. Some major elements (Ca, HCO 3 -, Mg), the dominant water type, display limited range of variation whereas for others (Na, Cl -) the scattering is wider (3 orders of magnitude). Only one sample for Cl and two samples for NO 3 - are above the recommended EU and Italian guidelines. Clear influence of bedrock geology and/aquifer composition is clear for some elements (e.g. As, F, Rb, V, U), other elements are indicator of mixing with deep formation water or sea-spray contribution (e.g. Br, I), others reflect also peculiar geographic area (e.g. B in Tuscany, Se in Emilia-Romagna). Factor analysis enabled the identification of a "corrosion" factor which includes Pb, Zn, Cd, Cu, Mn, Sn and Fe, all elements which are preferentially related to interaction with the distributing system pipelines