This paper concerns the evolution of the quality of the groundwater bodies over space and time, with special focus on nitrate. This case study deals with the qualitative status in alluvial-pyroclastic groundwater bodies located near Naples (southern Italy). The study is based on a significant hydrochemical database, gathered through: (i) groundwater sampling and water level monitoring, (ii) chemical analyses (Mg, Ca, K, Na, Cl, HCO₃, SO₄, NH₄, F, Li, Br, metals) and (iii) isotopic analyses (?¹⁵N and ?¹⁸O in NO₃, ?¹⁸O and ?D in water). Such data, processed using maps and graphical elaborations, has been very useful for identifying groundwater nitrate contamination. Finally, the application of isotope techniques has been important for understanding and following the trend of possible attenuation processes of nitrate content in groundwater. 

This paper concerns the evolution of the quality of the groundwater bodies over space and time, with special focus on nitrate. This case study deals with the qualitative status in alluvial-pyroclastic groundwater bodies located near Naples (southern Italy). The study is based on a significant hydrochemical database, gathered through: (i) groundwater sampling and water level monitoring, (ii) chemical analyses (Mg, Ca, K, Na, Cl, HCO₃, SO₄, NH₄, F, Li, Br, metals) and (iii) isotopic analyses (?¹⁵N and ?¹⁸O in NO₃, ?¹⁸O and ?D in water). Such data, processed using maps and graphical elaborations, has been very useful for identifying groundwater nitrate contamination. Finally, the application of isotope techniques has been important for understanding and following the trend of possible attenuation processes of nitrate content in groundwater.