Assessment and spatial distribution of Natural Background Levels (NBLs) in groundwater affected by natural and anthropogenic contamination: a case study in southern Italy

Lo studio della qualità delle acque sotterranee, alla luce della normativa europea (Water Framework Directive 2000/60/CE e Groundwater Daughter Directive 2006/118/EC) nonché italiana (D.Lgs 152/2006 e D.Lgs. 30/2009), non può prescindere dalla valutazione dei valori di fondo naturali (natural background levels –NBLs-). Negli ultimi decenni, diverse metodologie per la valutazione dei NBLs sono state proposte, applicate alla scala del corpo idrico sotterraneo (come previsto da 2014/80/UE) o sito specifica. I valori di fondo hanno come obiettivo quello di fornire uno strumento di valutazione dello stato qualitativo delle acque sotterranee nel caso in cui elevati valori di concentrazioni di taluni elementi siano superiori a quelli previsti dalla legge (in Italia si fa riferimento al D.lgs. 31/2001), REF, per motivi legati a fattori naturali. In questa ricerca il concetto di NBL è stato rivisto nell’ottica dell’analisi spaziale. Attraverso l’uso dell’Indicator kriging, sono state redatte della mappe di probabilità al superamento del NBL e del REF. Tali carte si sono rivelate degli strumenti per: 1. Distinguere le aree in cui la contaminazione è antropica e aree in cui la contaminazione è naturale 2. L’applicabilità del valore di fondo calcolato per l’area in esame e quando considerare il valore di fondo in alternativa al valore REF. Le indicazioni fornite dalle mappe sono dei supporti per la pianificazioni di ulteriori indagini e studi alla scala locale. La metodologia è stata applicata alla porzione meridionale del corpo idrico sotterraneo della Piana del Volturno –Regi lagni (quella in sinistra idrografica), in quanto presenta, per le sue peculiarità idrogeologiche, una contaminazione naturale diffusa nonché localmente fenomeni di contaminazione antropica. L’area inoltre è di grande interesse in quanto ricade in un sito di interesse regionale (Litorale Domizio-Agro Aversano), ed è stata soggetta negli ultimi anni a diversi studi mirati alla riqualificazione e bonifica dell’area

The hydrogeological monitoring of an experimental site in Campania focused at the evaluation of the contaminants transfer from the soil

Hydrochemical model , pyroclastic rocks, recharge time, Teverola, Campani

Using statistical analyses for improving rating methods for groundwater vulnerability in contamination maps

With the aim of developing procedures coping with the disadvantages and emphasising the advantages of existing rating methods and the use of statistical methods for assessing groundwater vulnerability, we propose to combine the two approaches to perform a groundwater vulnerability assessment in a study area in Italy. In the case study, located in an area of northern Italy with both urban and agricultural sectors, keeping the structure of the DRASTIC rating method, we used a spatial statistical approach to calibrate weights and ratings of a series of variables, potentially affecting groundwater vulnerability. In order to verify the effectiveness of these procedures, the results were compared to a non-modified approach and to the map resulting from the ‘‘Time–Input’’ method, highlighting the advantages that can be obtained, and defining the general limit of these applications. The revised method shows a more realistic distribution of vulnerability classes in accordance with the distribution of wells impacted by high nitrate concentration, demonstrating the importance of taking into account the specific hydrogeological conditions of the area

Groundwater Mass Balance in Urbanized Areas Estimated by a Groundwater Flow Model Based on a 3D Hydrostratigraphical Model: the Case Study of the Eastern Plain of Naples (Italy)

Since 2001, a rising water table occurred in the eastern part of the city of Naples (Italy), leading to flooding of the foundations of many buildings and of the underground infrastructures (garages, subway tracks, etc.). This resulted from the reduction in the exploitation of water for industrial use and drinking water in the central part of the groundwater body of the eastern plain of Naples: the groundwater withdrawal decreased from up to 3 m3/s in 1990 to a few hundred litres per second in 1998. The variation of piezometric levels led to flooding of foundations of many buildings and of underground infrastructures, this is a big amount of water lost by the aquifer system and that should be evaluated. In order to assess aquifer hydraulic features and the groundwater quantitative status, a 3D hydrostratigraphic model reconstruction was developed to support groundwater flow modeling and the evaluation of the groundwater balance. The 3D hydrostratigraphic model reconstructed the subsoil of the study area: layers of tuff and lenses of peat, which play an important hydrogeologic role as aquitard and aquiclude, are faithfully defined. Indeed, the model allows the depiction of the horizontal extension and of the thickness of each hydrofacies, even if strongly heteropic. The groundwater flow model was defined using the 3D hydrostratigraphic model in the construction of the geometry and assignment of hydrodynamic parameters. The calibration and sensitivity analysis prove the goodness of the assigned hydraulic conductivity values. The model, together with a detailed computation of the paved areas with reduced infiltration, evaluated the recharge in 0.101 m3/s. The model calibration assessed an evaporation rate lower than the prefixed value, probably due to the absence of vegetation that restricts the phenomenon almost exclusively to evaporation. Moreover, the calibration of the model confirmed: - the assumed groundwater flow towards the sea in 0.313 m3/s; - the hypothesized amount of the subsurface inflow from upstream in 0.504 m3/s. A considerable amount of water lost by the aquifer system, about 0.315 m3/s, could be used by Municipality for different public uses

Vulnerability mapping of groundwater contamination based on 3D lithostratigraphical models of porous aquifers

The aim of this paper is to apply a methodology in order to reconstruct a lithostratigraphic 3D model of an aquifer so as to define some parameters involved in the evaluation of the aquifer vulnerability to contamination of porous aquifers. The DRASTIC, SINTACS and AVI methods have been applied to an alluvial coastal aquifer of southern Italy. The stratigraphic reconstruction has been obtained by interpolating stratigraphic data from more than one borehole per 2 square kilometres. The lithostratigraphic reconstruction of a 3D model has been applied and used for three-dimensional or bidimensional representations. In the first two methods, the layers of the vadose zone and the aquifer media have been evaluated not only by the interpolation of the single boreholes and piezometers, but also by the 3D model, assigning the scores of the parameters of each layer of the 3D model. The comparison between the maps constructed from the weighted values in each borehole and the maps deriving from the attribution of the values of each layer of the 3D model, highlights that the second representation avoids or minimizes the “bullseye” effect linked to the presence of boreholes with higher or lower values. The study has demonstrated that it is possible to integrate a 3D lithostratigraphic model of an aquifer in the assessment of the parameters involved in the evaluation of the aquifer vulnerability to contamination by Point Count System methods

The role of 3D lithostratigraphical model as a tool in groundwater vulnerability mapping

The aim of this paper is to apply a computer based methodology in order to reconstruct a lithostratigraphical 3D model of an aquifer so as to define some parameters involved in the evaluation of the aquifer contamination vulnerability. The resulting vulnerability maps demonstrate that parameter layers prepared using the 3D model generate gradually changing boundaries between vulnerability classes. Sudden changes caused by data points are avoided. The main stratigraphical variations are along vertical paths, as expected in the sedimentation phenomena

Natural background levels for some ions in groundwater of the Campania region (southern Italy).

The aim of the study was the determination of the Natural Background Levels (NBLs) for the ions Na+, Cl-, SO42-, As3+, F-, Fe2+ and Mn2+, in some groundwater bodies of the Campania region (southern Italy). The “Protocol to evaluate the natural background concentrations” proposed in 2009 by ISPRA (Italian Institute for Environmental Protection and Research) has been applied to the chemical data set of groundwater of the examined groundwater bodies. These analysis have also been examined following the guidelines of the BRIDGE project (Background cRiteria for the IDentification of Groundwater thrEshold). These approaches to evaluate the Threshold Values (TVs) and the Natural background levels (NBLs), based on probability distribution functions, have been applied in many countries by various authors during the last five years. Changes applied to ISPRA Protocol in this study concern mainly the preselection criteria, in particular threshold values of specific ions, deriving from the aquifers geochemical features. The preselection criteria of the ISPRA Protocol have been merged with those of the BRIDGE Project in order to define a procedure suitable for the definition of the natural background levels (NBLs) in the examined aquifers. The Natural background level of fluoride for the “Phlegrean Fields” and the “eastern Plain of Naples” groundwater bodies shows values deeply exceeding the reference value (REF) of 1500 μg/L, ranging between 3600 μg/L and 15000 μg/L. The cause of this very high fluoride content is in the natural features of the aquifers constituted by volcanic and pyroclastic rocks. The volcanic origin of the aquifers is also the reason for the high arsenic content in “Phlegrean Fields” groundwater. Here the Natural background level calculated was about 47 μg/L against the drinking water standard value of 10 μg/L. The widespread high content of manganese and iron for the groundwater body of the “eastern Plain of Naples” is due to the reducing conditions related to the extensive marshlands present in the past. The very high Natural background level of all the examined ions for the groundwater body of “Ischia Island” depends on the existence of a geothermal system

Natural background concentrations for some ions in groundwater of the Campania region

The aim of the study was the determination of the natural background concentrations for the ions iron, manganese, arsenic and fluoride in some groundwater bodies of the Campania region. The natural background concentrations found often exceeded the threshold values established by international and national regulations (WFD - 2000/60/EC; GWDD-2006/118/EC; D.Lgs 152/06 and D.Lgs. 30/09).In this study the “Protocol to evaluate the natural background concentrations” proposed in 2009 by ISPRA (ISPRA, 2009) has been applied to the chemical data set of groundwater of the groundwater bodies

A 3D hydrostratigraphic model as a support to a groundwater flow model in an urban environment

Nella piana ad oriente di Napoli, la progressiva riduzione dei prelievi di acque sotterranee ad uso industriale e idropotabile ha provocato, durante gli ultimi 15 anni, la risalita della falda con conseguenti rilevanti problemi su aree assai vaste. In particolare nell’area ad est di Napoli la falda intercetta le fondazioni di molti edifici e alcune infrastrutture sotterranee (garages, binari della metropolitana, ecc.). Al fine di fronteggiare il problema e/o per definire un possibile utilizzo di questo surplus di acque sotterranee, è necessaria un’accurata conoscenza dell’idrogeologia locale e dell’assetto litostratigrafico. A tal proposito è stato ricostruito un modello litostratigrafico 3D propedeutico allo sviluppo di un modello di flusso nell’area di studio, con soddisfacenti risultati

Hydrostratigraphical setting and groundwater quality status in alluvial aquifers: the low Garigliano River Basin (Southern Italy), case study

The study aims at applying a 3D lithologic model for the characterization of the Garigliano River plain aquifer and the assessment of the nitrate contamination risk . The risk map obtained presents a good spatial correlation with the nitrate content of the aquifer highlighting the sectors more affected by nitrates and supporting the individuation of the source of nitrate contamination. This suggests that the source of the groundwater nitrate is prevalently related to intensive cropping or livestock. The paper highlights the great advantage to use a 3D model of the subsoil of a alluvial plain (Garigliano basin) and the great results that it is possible to achieve. Indeed, the author would stress that the originality of this paper lies not in the application of the method to assess nitrate contamination risk, but rather in his application directly by the 3D lithostratigraphical model