The Campanian Plain (CP) shallow aquifer (Southern Italy) represents a natural laboratory to validate geochemical methods for differentiating diffuse anthropogenic pollution from natural water-rock interaction processes. The CP is an appropriate study area because of numerous potential anthropogenic pollution vectors including agriculture, animal husbandry, septic/drainage sewage systems, and industry. In order to evaluate the potential for geochemical methods to differentiate various contamination vectors, 538 groundwater wells from the shallow aquifer in Campanian Plain (CP) were sampled. The dataset includes both major and trace elements. Natural water-rock interactions, which primarily depend on local lithology, control the majority of geochemical parameters, including most of the major and trace elements. Using prospective statistical methods in combination with the traditional geochemical techniques, we determined the chemical variables that are enriched by anthropogenic contamination (i.e. NO3, SO4 and U) by using NO3 as the diagnostic variable for detecting polluted groundwater. Synthetic agricultural fertilizers are responsible for the majority of SO4 and U pollution throughout the CP area. Both SO4 and U are present in the groundmass of synthetic fertilizers; the uranium concentration is specifically applicable as a tracer for non-point source agricultural fertilizer contamination. The recognition of non-geological (anthropogenic) inputs of these elements has to be considered in the geochemical investigations of contaminated aquifers.

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 SO 4 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 (NO 3 -, SO 4 2-, NH 4 ? ), 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.