FIRST RESULTS ON THE GEOCHEMICAL CHARCTERIZATION OF SOME ARSENIC CONTAMINATED GROUNDWATER TO BETTER ADDRESS THEIR EXPLOITATION FOR CIVIL USE

Exploitation of arsenic contaminated groundwater in Viterbo region of Central Italy has been suspected to cause adverse health effects among the population. This paper focuses the recent status of knowledge about arsenic in groundwater of Viterbo Region. This area is located between the Tyrrhenian Sea coast and the Central Apennines mountains, and was formed by volcanic activities (acidic and K-alkaline magmatism) in the late Pliocene - Pleistocene period, and lays on the sedimentary basins of upper Miocene-Pleistocene age, elongated between ridges of Mesozoic- Paleogene sedimentary rocks, the latter overlying a Paleozoic-Triassic metamorphic basement. They have been analysed data coming from over then 200 different groundwater sources including wells and springs, located in the whole region of Viterbo. During sample collections from 2007 to 2009, a series of in-situ measurements were conducted: pH, electrical conductivity, total dissolved solids (TDS), temperature, redox potential (Eh) and alkalinity. The concentrations of major anions (Cl−, NO3− and SO42−), cations (Na+, K+, Ca2+, Mg2+ and NH4+), arsenic and other trace element were determined by laboratory analysis. The target of this study has been the interpretation of these properties and the geochemical modelling of them to better address the groundwater exploitation for domestic use in the area. All of the available existing arsenic data sets have been collated and collected and incorporated into a Geographical Information System (GIS) system for production of maps to highlight environmental contamination and processes or distribution of As in groundwater. Graphical relationship between the concentrations of arsenic were correlated with major cations and anions, measured in groundwater used for domestic supply, to identify the source and mechanism of arsenic release in the volcanic and sedimentary aquifers of Viterbo Region. The identified hydrofacies have been integrated into GIS system to show the distribution of the dominant facies for each municipality. For each resource, hydrofacies and arsenic concentrations have been correlated to understand relationship between the enrichment of arsenic in groundwater on the different facies properties. Some interesting results came out to address the groundwater exploitation