R. COSSU, L.E. ZUFFIANO', P.P. LIMONI, G. DE GIORGIO, P. PIZZARDINI, T. MIANO, D. MONDELLI, R. GARAVAGLIA, C. CARELLA, M. POLEMIO, 2017, Geochemical and hydrogeological study to identify the source of nitrate in the carbonate groundwater (Southern Italy), Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium, Cagliari, 2 - 6 October 2017,
URL: http://www.cnr.it/prodotto/i/375619

Where the unique natural water resource is groundwater, is the case of wide karstic area, the attention and the susceptibility of local communities and authorities to groundwater risks can be so high to determine relevant misunderstanding due the existence of a number of landfills. For solve this kind of situation, a multi-methodological approach is proposed with the purpose to clarify the role of landfill leakage in terms of groundwater quality degradation risks. The selected study area (SSA) is narrow portion of a wide and deep coastal karstic aquifer, for these characteristics to be considered a case of high complexity and susceptibility. Mainly nitrate and secondly iron groundwater concentration were considered anomalously high in some well of the SSA, not far from Bari (main town of Apulia, a region of Southern Italy), worried about the potential effects of some landfills located in SSA. Five landfills have operated from 1975, one after the other, using increasing safety and technological devices to reduce risks due to leachate leakages with consequent groundwater quality degradation. The multi-methodological approach, which could be potentially applied worldwide, includes_ the hydrogeological site characterization; the chemical study and the multi-isotope characterization of groundwater and leachate; the land use analysis and the estimation of nitrogen contributions deriving from agricultural activities, focusing on the use of fertilizers; the mineralogical study of groundwater suspended particles to define the origin of some substances, focusing on iron and manganese, relevant for the SSA. The hydrogeological site characterisation highlighted the local peculiarties of the aquifer. The chemical study was focused on the most important chemical features (Ca2+, Mg2+, Na+, K+, Cl-, SO4 2-, NO3 -), especially to define geochemical peculiarties, along with some minor chemical elements were taken into account, to define globally the groundwater quality and the leachate characteristics. The environmental isotopes of hydrogen (H), carbon (C), nitrogen (N) and oxygen (O) were used to identify the groundwater provenance and the most relevant geochemical reactions. The oxygen-18 (18O) and deuterium (2H) stable isotopes were used to investigate the origin of water in the aquifer system of the study area. The combination of NO3 - concentration with ?15N-NO3 - and 18O-NO3 - in groundwater also provides valuable information for identifying the true sources of anthropoghenic NO3 -. Groundwater and leachate samples were analysed for 13C and Tritium (3H), completing the framework of knowledge on the role of leachate on groundwater as previous studies have demonstrated that the biogeochemical processes occurring within the landfill environment can produce a unique composition of these isotopes and therefore they can be utilized successfully to delineate the potential leachate influence. The land use analysis highlighted quantity and type of used fertilizers permitting to compare these with groundwater in terms isotopic signature. The mineralogical study demonstred the role of suspend natural parcticle due the presence of terre rosse (red clays) in some groundwater samples. The approach confirmed globally, meaning with all the defined results, which are not quality degradation effects on the sampled groundwater.

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