Geochemical characteristics of waters in mineralised area of PeloritaniMountains (Sicily, Italy)

This paper presents the results of a study on the geochemistry of waters circulating in the mineralisedarea of the south-eastern sector of Mt. Peloritani (north-eastern Sicily, Italy), aimed at basic understandingof the geochemical processes influencing their chemical composition. Chemico-physical parametersand data on 26 major and minor chemical elements are reported for 103 water samples. Water chemistryis mainly dominated by dissolution of carbonates and hydrolysis of aluminosilicate minerals. Total dissolvedsalts (TDS) range from 80 to 1398 mg/L. All the waters exhibit EH characteristic of an oxygenatedenvironment. Excluding two samples, which show very high H+ activity (pH = 3.0 and 2.7), all the watershave pH values in the range 6.2–8.6. Cluster analysis based on major ion contents defined three mainchemical water types, reflecting different hydrochemical processes. The first, group I, has low salinity(average TDS = 118 ± 30 mg/L) and abundance orders (meq/L) Na > Ca Mg > K and Cl HCO3 > SO4.With increased water–rock interaction, waters in groups II and III become more saline, changing compositiontowards SO4–Cl-alkaline earth and HCO3-alkaline earth types. Weathering of carbonate mineralscauses waters to become saturated with respect to calcite and dolomite, whereas the incongruent dissolutionof aluminosilicate minerals causes the solution to reach equilibrium with kaolinite and to formsmectites. Trace element geochemistry in the analysed waters reflects interactions between watersand existing mineralisation, with elemental concentrations showing highly variable values, and higherconcentrations of As, Pb, Sb and Zn near known mineralisation. Lead–Zn and As–Sb statistical associations,probably distinguishing interactions with different mineralogical phase paragenesis, were revealedby factor analysis. The main aqueous chemical forms of trace elements predicted by chemical speciationcalculations are also reported. As most of the analysed spring waters provide the main source of freshwaterfor domestic purposes, attention should be given to As and Sb, whose concentrations exceed the recommendedlimits.