Discharge areas of carbonate fractured and karstified aquifers are a sensitive system of great interest, where frequently groundwater resources are tapped for drinking water supply. In geological settings affected by recent and/or active tectonics, mixing between fresh water coming from recharge areas and groundwater from deeper circuits, influenced by raising fluids, influences hydrogeochemistry. Surveys on major ions, trace elements and stable isotopes have been performed in the San Vittorino Plain (Central Italy), where the major source of drinking water for Rome is located (Peschiera Springs, mean discharge 18 m3 s−1, half of them tapped). Results of 21 springs revealed different contribution from recharge areas and deep flow paths, by increasing salinity and ion content, with particular references to Ca2+, HCO3 − and SO4 2−. Three main groups, respectively, related to fresh waters from recharge areas, groundwater from deep contribution and a mixing group between them, have been identified. Water stable isotopes allow to identify the common origin from rainfall and a very steady contribution with seasons and year, due to the huge extent of recharge area (>1000 km2). Saturation Indexes gave insight on the contribution of deep fluids, mainly CO2 and H2S, which turned groundwater to undersaturated conditions, facilitating rock dissolution. By PHREEQC software, the mixing between two considered end-members has been simulated, evaluating about 25% of deep contribution in the basal springs of San Vittorino Plain. Chemistry of Peschiera spring reveals a very limited percentage of deep flow paths (10%), which can lead to slight hydrochemistry changes even in possible drought conditions, when discharge can decrease until 15 m3 s−1
Groundwater beneath a municipal solid waste landfill area in central Italy has been studied. The study included two sampling events: in June and October 2014. The aim of this study was to determine the quality of groundwater and to test the use of boron and tritium isotopes as tracers of contamination due to the presence of the landfill. The results of chemical analyses indicate that the samples collected from boreholes located downgradient from the landfill are contaminated. The principal contaminants are Cl-, NH 4 + , Fe, As, Cr, B, Hg and Zn, which were detected at maximum levels during the June sampling event. The boron and tritium isotopic composition of the collected water samples was analysed to evaluate the source of contamination. The results indicated a δ 11 B value of 19.31‰ for uncontaminated groundwater, while δ 11 B values between 4.37 and 9.41‰ were reported for contaminated groundwater. The correlation between boron and chloride provided a basis for evaluating the plume direction. Tritium (3 H) isotopes were analysed during the second sampling event (October). The results indicate that 3 H values ranging between 2.7 and 3.6 TU were reported for uncontaminated waters; this groundwater has a short residence time in the aquifer. A 3 H value of 34.5 TU was reported for one groundwater sample (Sample 7). This value is indicative of contamination by landfill leachate.
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