HYDROGEOLOGY AND HYDROGEOCHEMISTRY OF THE GARIGLIANO RIVER PLAIN (SOUTHERN ITALY)

In the Garigliano river plain NO3 and Fluoride contents often and widely exceed the drinking-water quality guidelines of 50 and 1,5 mg/L. The Fluoride content is strictly related to the piezometric pattern. Close to the Garigliano river, lower nitrate content is related to reducing conditions, testified by low values of SO4 and high content in Fe and Mn. Afterwards, the isotopic analysis (15N/14N and 18O/16O ratios of dissolved nitrate) were carried out by the CNR-Roma in groundwater of some wells. Starting from this broad hydrogeological knowledge, the following maps to evaluate the “Contamination risk” were drawn up: • the “Pollution Vulnerability Map”, evaluated by the SINTACS parametric system; • The “Agricultural Hazard Map”, rated by the parametric models IPNOA (Danger Index by Nitrates of Agricultural Origin). The good correlation between the “Potential Agricultural Nitrate Contamination Risk Map” and the nitrate content distribution suggests that the source of the groundwater nitrate is chiefly related to intensive cropping or livestock. The results of isotope analysis confirm the hypothesis of the agricultural origin of nitrates and the validity of the use of parametric methods at medium/small scale to individuate the source of nitrate in groundwater