Hydrogeological and hydrochemical observations on salinization processes in the coastal Campidano Plain (south-eastern Sardinia).

The Soutbem Campidano Plain is located in the eoastal area of the eastem part of the Gulf of Cagliari. Mainly eomposed of Tertiary and Quatemary sediments, this plain is bordered to the north and the east by Palaeozoic sehist and granites. Groundwaters oeeurring in different aquifers of the Plain are affeeted by salinisation. This study aimed at defining the role of both sea water intrusion and other sourees of salts in the oceurrenee of this peeuliar high salt content in produetive groundwater wells of the area, tapping both the shallow aquifer and tbe eonfined or semi-confined multi-Iayered aquifer oecurring in the Miocene marly-arenaeeous sequenee. Besides the data referring to a monthly monitoring of a large number of wells for conduetivity and piezometrie levels, ehemieal analyses of seleeted groundwater samples were available. The interpretation of the chemieal data, together witb some hydrogeologieal observations, led to exc1ude the hypothesis that the salinisation of the aquifers is caused only by present marine intrusion. In most eases the salinisation has to be attributed to solution of salts present in the Mioeene deposits whiehsuperimposes, or not, on sea water intrusion. Furthermore a series of ehemieal proeesses, sueh as ionie exehange or sulphate reduetion, entangle both type of salinisation