and includes, from north to south, Castell’Azzara, Semproniano, Catabbio, Sorano, Sovana, Pitigliano e Saturnia communes in the Grosseto province, and Castelfranco Ischia di Castro, in the Viterbo province.

Abstract

The present work regards the study of water’s geochemistry of an Southern Tuscany area, between two volcanic complexes: Monte Amiata to the north and Monti Vulsini (Latera) to the south-east.

The sampling site covers an area of 225 Km

and includes, from north to south, Castell’Azzara, Semproniano, Catabbio, Sorano, Sovana, Pitigliano e Saturnia communes in the Grosseto province, and Castelfranco Ischia di Castro, in the Viterbo province.

The study of water provided the sampling of 46 samples, including springs and wells in the area of study, to determine the physical-chemical characteristics and to identify the aquifers within which are circulated,. Most of the well water samples comes from Pitigliano and surroundings areas.

The chemical and physical parameters that may change during transport from the sampling site to the laboratory, were determined directly in the field, such as pH, temperature, electrical conductivity and alkalinity.

All other analysis was performed in the laboratory waters of the Earth Sciences Department of Pisa: the determination of cations and anions in solution was performed by ion chromatography, while the content of silica, boron, ammonia and iodine were determined by spectrophotometry.

Several diagrams were adopted for the classification of water: the Ludwig- Langelier square diagram, the triangular diagrams (of the anions and cations), and the Schoeller diagram.

These diagrams have identified three chemical families of water: Ca-HCO3 water, Ca-Na-HCO3 water and Ca-SO4 water. The results of such analysis associated with the study of geology and permeability of the formations outcropping in the study area allowed defining the main circuits of the water sampled.

The Ca-SO4 waters, at higher salt content and temperature, circulate in the carbonate-evaporite formations of the Tuscan sequence.

The Ca-Na-HCO3 waters circulate within the volcanic rocks, that cover the eastern sector of the study area and related to the volcanic complex of Mt Vulsini.

Instead, the Ca-HCO3 waters, circulate in the sedimentary formations and in the

same volcanic rocks.

The application of various methodologies thermometric suggested temperatures

between 50 e 70°C for a potential geothermal reservoir in this area.