Differentiating natural and anthropogenic impacts on water quality in a hydrothermal coastal aquifer (Mondragone Plain, Southern Italy)

Groundwater from the Mondragone Plain (Southern Italy) has been investigated by a monthly sampling regimen over the course of a hydrologic year in order to analyze geochemical signatures and has been experienced methods for detecting natural and anthropogenic contamination dynamics that affect resources for human water supply. The Mondragone Plain aquifer is characterized by (1) anthropogenic land uses, (2) varying degrees of hydrothermal interactions, and (3) the potential for seawater intrusion. Anomalies induced by anthropogenic pollution produce non-normally distributed time series and an alteration of the natural SO4 (2-) background of groundwater. Variables depending on natural processes are related to water-rock interactions along groundwater flow path, i.e., the hosting aquifer lithology of hydrothermal systems, the recharging massifs of Mt. Petrino and Mt. Massico, and more recent volcanic and alluvial formations. Solute transport in groundwater affects the urban aquifer, both by mixing of thermal waters and by ions deriving from agricultural activity (NO3 (-), SO4 (2-), NH4 (+)), compromising the quality of a resource largely used by locals. The two thermal systems in the studied area [Levagnole and Padule-San Rocco] are two different aquifers with an independent circulation and chemical composition. Seawater intrusion, both into thermal systems and into shallow aquifers, seems to be unlikely despite the detected increase of salinity in the LEV system close to the shoreline.