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The migration of a groundwater contaminant plume consisting of light nonaqueous phase liquids (LNAPLs) along the Ionian coastline of Sicily, Italy, has been reported to follow a trajectory that is inconsistent with the regional hydraulic gradient. The influence of several faults affecting the fractured carbonate bedrock aquifer, and groundwater abstraction from a well, were hypothesized to be responsible for the anomalous trajectory of the contaminant plume. A conceptual hydrogeological model was developed for the study area that incorporated structural information derived from geophysical surveys and the mapping of fractures in bedrock outcrops. This conceptual model was incorporated into numerical groundwater flow and solute transport models to simulate the groundwater transport of the light nonaqueous phase liquids. Four model scenarios representing different levels of complexity were tested to assess the relative influence of geological heterogeneity and groundwater abstraction on the migration of the contaminant plume. Results show that underground major discontinuity systems, invoking the presence of the faults in the model domain accounted for the observed migration of the contaminant plume, act as conduits for groundwater flow. Conversely, groundwater abstraction from a well was found to result in relatively minor, localized impacts to the migration of the contamination plume. This study demonstrates the importance of incorporating geological heterogeneity into groundwater modelling and environmental risk assessments associated with the storage of LNAPLs. [ABSTRACT FROM AUTHOR]

Hydrochemical and geophysical methods were used to assess saline paleo-water mass transfer induced by piston flow in the alluvial aquifer of the Oltrepò Pavese plain (northern Italy). The surface aquifer shows salinity contamination from a Tertiary substrate of marine origin, due to mixing of the shallower fresh groundwater with the Po Plain's deep brines. The study also used continuous monitoring of groundwater electrical conductivity, temperature and piezometric levels. Well logging and geophysical imaging, conducted at different times, revealed that the contamination varies over time, and that the water salinity and the depth of the transition zone (between the surface freshwaters and the deep saline waters) are subject to modifications. This is due to a pressure transfer—and, subsequently, mass transfer−from the groundwater circuits of the nearby Apennine mountains. It suggests that a hydraulic connection exists between the fractured Apennine water circuits and the deeper Mio-Pliocene and Tertiary saline-water circuits found below the plain's alluvial aquifer. Coinciding with significant recharge episodes that affect Apennine water circuits (prolonged rainfall and snow melt at mid-high altitudes), there is a pressure transfer transmitted along the water circuits in which saline water resides, providing an impulse to rise along the discontinuities and reach the alluvial aquifer. The conceptual model is supported by evidence that wells constructed in correspondence to hydraulically active tectonic discontinuities are affected by the arrival of saline waters with variable delays, while wells sited in sectors not affected by tectonic discontinuities are diluted by 'fresh' waters connected to alluvial aquifer recharge. [ABSTRACT FROM AUTHOR]

The Maggiore Valley well field plays a fundamental role in supplying drinking water to a large territory of the Piedmont Region (northwestern Italy) and has been intensively exploited since the early twentieth century. This water resource is hosted in a deep, multilayered aquifer system. The main purpose of this study was to characterize the recharge processes of the deep aquifer through hydrochemical and isotopic assessments, as well as the water quality in the recharge and drainage areas. For this purpose, 128 physical–chemical analyses (major ions) and 50 isotopic analyses (δ18O and δ2H) were carried out on samples collected in shallow and deep aquifer complexes in two sampling campaigns in 2021. From the results, a hydrogeological conceptual model of recharge processes was developed. The chemical data confirm the presence of bicarbonate–calcium facies in most samples of the shallow and deep aquifer complexes. Clear hydrochemical differences were observed among the investigated sectors. The recharge areas were identified as (1) far zones, namely the shallow aquifer complex of the Cuneo Plain, and (2) the shallow and deep aquifer complexes with groundwater mixing in the riverside sector of Po Plain in the Turin area. The mixing of waters from the Cuneo Plain and Turin Plain was verified in the well field area. The isotopic values of the artesian well water also confirmed contributions from the Turin and Cuneo Alps. This study clarified the recharge processes, thereby defining potential pollutant pathways, and the results provide additional support for groundwater resource management and protection. [ABSTRACT FROM AUTHOR]

The assessment of groundwater vulnerability is an important aspect of territorial planning aimed at the management and protection of groundwater quality. This topic is particularly relevant for the Campania region (southern Italy) due to the abundance of groundwater resources and the strong dependence on them of current economic, social and environmental settings. The region is characterized by complex geological, structural and hydrogeological frameworks which make challenging and innovative the assessment of groundwater vulnerability with SINTACS, a parametric method officially recognized by the Italian environmental agencies. In order to apply results obtained to current regional regulations, groundwater vulnerability was estimated for the 80 principal aquifers, hosting respective groundwater bodies, as recognized by the application of the Directive 2000/60/EC. Among principal results, the alluvial and limestone (karst) aquifers, which are the most productive of the region, show the highest groundwater vulnerability, even with spatially variable conditions depending on local hydrogeological features. [ABSTRACT FROM AUTHOR]

Understanding the spatial variations in groundwater chemistry is fundamental to assess the groundwater pathways and identify the most advantageous strategies for a sustainable use of groundwater resources. In fact, such variations can be the result of the complex structure of flow systems or local pressures of natural or anthropic origin. Thus, a detailed analysis of spatial variations in hydrochemical data provides an insight into natural and anthropogenic effects on groundwater quality and into scale-dependent heterogeneity. Multivariate statistics and, in particular, clustering methods can effectively support those analyses, as remarked by a large number of studies in the literature. However, open issues still affect the reliability and general applicability of multivariate statistics and cluster analysis in hydrogeology, especially if a limited number of data and information about well-casing and screen characteristics are available. Such questions are related to the appropriate selection of end-members on one hand, and to the subjectivity of clustering results on the other hand. Starting from hydrogeological data of the Solofrana River basin in Southern Italy, the present paper illustrates an original approach to end-member selection in a pyroclastic-alluvial aquifer, and to the analysis of the geochemical evolution of groundwater in a given basin based on k-means clustering. The proposed approach has been applied to a real dataset collected in July 2010. Comparing the results against classical hydrogeological models and graphical methods typically used to classify water samples, a robust validation of the methodology has been achieved. • A new method to define groundwater end-members in complex aquifer systems is proposed. • An original vector index (EMAC), based on groundwater composition indices, is defined. • The vector index yields a significant data reduction in view of k-means clustering. • Physical insight on EMAC allows a clever selection of initial centroids. • Validation of the method is based on silhouette values and physical models. [ABSTRACT FROM AUTHOR]

In the densely urbanised Milan Metropolitan area (northern Italy), the long history of anthropogenic activities still exerts a significant pressure on groundwater resource. One of the most serious threats to the water quality of urban aquifers is attributed to diffuse contamination, which is caused by a series of unknown small sources (i.e., multiple point sources) distributed over large areas. In the study area and in many industrialised regions of the world, tetrachloroethylene [PCE], trichloroethylene [TCE] and hexavalent chromium [Cr(VI)] represent the common example of long-standing and persistent pollution in groundwater. In the Milan Metropolitan area, high levels of PCE + TCE and Cr(VI) were detected in the shallow aquifer as well as in the deep aquifer. To assess and map the shallow and deep aquifers susceptibility to PCE + TCE and Cr(VI) contamination at a regional scale, the Weights of Evidence modelling technique has been applied. This method has been used to objectively evaluate the spatial correlation between the high presence of these pollutants in each aquifer and hydrogeological and land use factors that can potentially influence the contamination. Moreover, the results allowed us to quantify on a large scale the effect that preferential flowpaths, due to both thickness variation in the aquitard and the areal density of multi aquifer wells, have in reducing the protection of the underlying deep aquifer. The end-products of the study constitute a key tool to be used by water-resource managers and decision-makers for the improvement of groundwater management and protection strategies. • Multi-source diffuse pollution seriously threatens water quality in the Milan area. • Shallow and deep aquifers susceptibility to PCE + TCE and Cr(VI) pollution is mapped. • The effect of hydrogeological and land use factors is quantified at a regional scale. • The influence of aquitard heterogeneities and multi-aquifer wells is investigated. [ABSTRACT FROM AUTHOR]

In a volcanic-sedimentary aquifer in central Italy, we investigate the co-existence of arsenic and fluoride in groundwater, aiming at identifying the most probable processes deductible at regional/groundwater body scale leading to the observed co-contamination in groundwater. Further, the areas at risk for human health where high concentrations can produce a significant risk to human health have been investigated. The study area is located in Latium (Central Italy) where silica-undersaturated alkali-potassic formations of Plio-Pleistocene age largely outcrop above marine and continental sand and clay deposits (Neogene) and continental alluvial deposits (Lower Pleistocene–Middle Pleistocene). Geochemical data from groundwater at 322 wells and 76 springs have been analyzed through statistical methods including clustering/PCA and geostatistical analysis. The results show exceedances of the drinking water standards for F (1.5 mg/L) and As (10.0 μg/L) in 29% and 55% of the sampled groundwater, respectively. Multivariate statistics suggest a widespread process of water-rock interaction with the K-alkaline volcanic formations releasing As, F, K, Si, V, Rb and PO 4 to the groundwater. As and F show a good correlation (Pearson's r = 0.61, Spearman's r s = 0.59) and define a separate PCA component, confirming that their background in groundwater might be governed by a common process. Kriging interpolations have been used to study the spatial distribution of the two parameters, identifying areas with the highest concentrations and highest probability of exceeding the standards for human consumption. Moreover, by resampling the As-F data with the jackknife technique it was possible to identify the variations of their correlation index in the study area, due to specific As or F anomalies. While in the peripheral areas of the volcanic districts, dominated by sedimentary deposits, the As-F correlation index does not present important fluctuations, Indicator Kriging shows specific As or F correlation anomalies within the volcanic groundwater bodies and along the Tyrrhenian coastline. These anomalies seem to correspond to the zones with the highest thermal flux and/or are located near important structural lineaments. Fluoride correlation anomalies close to mining sites (fluorite) have also been observed. We hypothesize that, unlike the regional co-contamination, these local anomalies are related to the upwelling of geothermal fluids along fracture/fault systems that mix with cold groundwater, or to the interaction with mineral deposits particularly enriched of these elements. • Arsenic-fluoride correlation in a volcanic-sedimentary aquifer in Italy is analyzed. • Water-rock interaction produces the As-F background and maintains their correlation. • Anomalies appear linked to interaction with geothermal fluids and/or mineral deposits. • Indicator kriging indicates the most suitable areas for drinking water exploitation. [ABSTRACT FROM AUTHOR]

• The wGHIN was presented as a refinement of the wGHI by Korbel and Hose (2017). • The wGHIN was first applied to European aquifers in nitrate vulnerable zones. • Minor deviations from good ecological status were detected in most of the sites. • The index is theoretically sounding, concrete, numerical and economically feasible. • The index showed a medium performance and requires taxonomic skills. The weighted Groundwater Health Index (wGHI), introduced by Korbel and Hose (2017), is a multimetric, two-tiered framework for measuring and identifying the ecological status of groundwater ecosystems using biotic and abiotic indicators. The wGHI was conceived and tested in unconsolidated alluvial aquifers in Australia. In this study we applied and tested the index in European unconsolidated aquifers located in nitrate vulnerable zones (NVZ). A refinement of the wGHI was necessary to ensure the compliance with the requirements of the European Directives. We called the refined index wGHIN where N stands for nitrates. We tested the wGHIN in an unconsolidated aquifer (VO_EU_GWB) in the River Vomano catchment (central Italy) that was designated NVZ in 2005 and has since been subject to management measures pursuant to the Nitrate Directive. We also monitored a complex of minor confined unconsolidated aquifers (VO_CON_GWB) located in the same catchment. The wGHIN highlighted extensive nitrate contamination in both the VO_EU_GWB and VO_CON_GWB aquifers. Despite the widespread contamination, most of the monitoring sites showed only minor deviations from good ecological status. The index also highlighted the biodiversity of the aquifers which happened to be among the most diverse in Europe. The wGHIN proved to be theoretically sounding, concrete, numerical and easily understandable by the public and policy-makers. Finally, the index was economically sustainable. The wGHIN has certain limitations that have to be resolved, such as the low correlation of some indicators to the index overall score in the aquifers of the River Vomano and the fact that the index is not "operationally simple" since it requires taxonomic and ecological skills. [ABSTRACT FROM AUTHOR]

• The 2016 earthquake in Central Italy reactivated normal faults with important coseismic ruptures. • The Nera River discharge increased followed by a fast depletion in 2017 and 2018 recession periods. • The increase in aquifer permeability seems affecting the post-earthquake river discharge. The 2016–2017 seismic sequence in Central Italy caused the reactivation of a complex NNW-SSE trending, WSW-dipping normal fault system associated with relevant coseismic ruptures. The seismic sequence significantly affected the groundwater circulation hosted in limestone aquifers. Based on the data available in May 2019, this work aims to contribute to understanding how the reactivation of the seismogenic faults has influenced the hydrological system of the upper Nera River basin. It appears that the seismic sequence changed the recession processes of the Nera River. Post-seismic recession curves are described by straight lines (non-darcian flow), while the pre-seismic ones follow the exponential function (darcian flow). After the earthquake, the system empties (i.e., the storage decreases) at a faster rate than before; this effect persists after more than two years from the 2016 earthquake. According to some geological cross-sections, the analysis of coseismic deformations and recession curves, a presumable increase in aquifer permeability seems to be the main factor affecting the post-earthquake river discharge. If the non-darcian recession process continues in the future, the river flow will be more variable than in the past, causing significant problems to water-using productive activities. This because, during prolonged drought periods, the fast decrease of the dynamic water storage would produce discharges lower than in the past. The results here reported can contribute to the understanding of the medium-long term evolution of this particular hydrological system as well as of other similar ones and could be useful to better managing the groundwater resources. [ABSTRACT FROM AUTHOR]

This study investigates for the first time the integrity of multiple stacked aquitards with different degrees of contaminant degradation. Aquitard integrity was assessed in a contaminated, multi-layered, alluvial aquifer-aquitard system (Ferrara, northern Italy). The system was contaminated by mixed organic contaminants of industrial origin (mostly chlorinated ethenes) that were illegally disposed in an urban dump four to five decades ago. High spatial resolution profiles of hydraulic head, geochemistry and chlorinated hydrocarbon concentrations were determined through the multi-layered system via discrete interval sampling of continuous cores and multilevel groundwater sampling, at three locations aligned along a transect adjacent to the buried waste to a maximum depth of 53 m below the water table. The profiles revealed that the two shallow aquitards had low integrity with respect to impeding downward migration of dense non-aqueous phase liquid (DNAPL), and provided little protection to the underlying aquifers against DNAPL contamination due to preferential pathways through imperceptible fractures and/or permeable micro-beds. However, both aquitards inhibited downward DNAPL migration to some extent due to DNAPL retention along its flow paths and accumulation at lower permeability interfaces, with decreasing peak concentrations at the top of successively deeper aquitard units. Moreover, both aquitards enhanced contaminant biodegradation due to the occurrence of organic rich sub-layers, influencing the contaminant plume composition, mobility and fate in the underlying and overlying aquifers. The deepest aquitard showed evidence of DNAPL accumulation at the top and slow diffusion-dominated transport consistent with 40 years of transport, suggesting higher integrity compared to the two shallower aquitards. However, the occurrence of micro-fractures and/or discontinuities in the aquitard upgradient under the dump (source) is the most likely explanation for contamination of the deepest aquifer. Analytical 1-D simulations of the diffusion profiles in the deepest aquitard revealed that DNAPL contamination down to the top of this aquitard occurred with minimal delay after DNAPL waste disposal began. The results highlight the necessity of high-resolution vertical profiling for assessing the presence of imperceptible features relevant to DNAPL migration and integrity of individual aquitards affecting organic contaminant source zone mass and phase distributions over decades. Image 1 • Organic contaminants migrated through three vertically stacked alluvial aquitards. • Aquitard integrity was assessed based on high-resolution vertical profiles of data. • Contaminant accumulation and retention occurred at all aquifer-aquitard interfaces. • An early contamination stage controlled distribution and fate of contaminants today. • Diffusion profiles were modeled to assess the first arrival of contaminants at depth. [ABSTRACT FROM AUTHOR]

Aquifer mismanagement is a common anthropogenic cause of subsidence and uplift phenomena in alluvial plains, representing one of the main natural hazards in urban areas due to related damage to urban structures and infrastructures. In this work, the groundwater rebound phenomenon that occurred in the last decades of the 20th century in the Lufrano area (Metropolitan area of Naples, Southern Italy) has been studied by integrating geological data, hydrogeological continuous monitoring and spaceborne SAR information derived from ERS-1/2 and ENVISAT satellites. In the period of 1989–2006, the Lufrano area, which hosts an important well field made up of 180 wells extracting groundwater for drinking use, suffered an initial over-exploitation of the aquifer which was followed by a sudden and severe decrease of the volume abstraction, resulting this last in a rapid ground uplift. The coupled analysis of hydrogeological and DInSAR data have shown a correspondence between piezometric level rise (up to 15 m) and ground uplift (up to 50 mm) trends in the period 1989–2006. In order to examine the spatio-temporal evolution of the phenomena and the cause-effect relationships, showing the link between the two phenomena and their rates, longitudinal cross-sections were carried out and comparisons between piezometric level rise and time-series of displacements were reconstructed. The obtained results represent an initial contribution to the definition of ground deformation related to groundwater level rise phenomena, providing a basis for future studies focused on the modelling of the hydro-mechanical properties of the aquifer. [ABSTRACT FROM AUTHOR]

Groundwater bodies are important water supplies since they represent the safest and most reliable sources for drinking water. They are also regarded as reliable "climatic archives", being able to "store" information on climate variability at both local and global climate conditions. The shallow aquifer hosted in the Mt. Amiata volcanics (Quaternary) represents the most important freshwater reservoir of southern Tuscany (central Italy), currently providing nearly 37•10^6 m3 of drinkable water to the inhabitants of both Southern Tuscany and Northern Lazio regions. Although hydrogeological and geochemical studies have been carried out in the last decades, this groundwater system is still poorly constrained and, thus, deserves to be further investigated in detail.The present work has a two-fold purpose aimed at: (i) reviewing the isotopic features characterizing the meteoric recharge over the area and (ii) tuning the circulation model in of the Mt. Amiata aquifer. Additional goals are to: (i) evaluate the response of this groundwater systems to climate changes, and ii) provide useful hints to the local authorities for future water management actions addressed at protecting this resource.Previous data were combined with those acquired with a network consisting of 8 different rain gauges (passive samplers) deployed from January 2017 to December 2018, over the Mt. Amiata area installed at different altitudes: between about 300 (foothills) and 1,700 m a.s.l. (mountain summit). The rainfall levels were monthly or bi-monthly measured along with the flow rates of selected springs. Rainfall and spring waters were collected for stable isotopic determinations (oxygen, deuterium) and tritium analyses and compared to those obtained from between December 2010 and January 2012 in same sites. In 2017 a significant decrease of precipitation with respect to those of 2011 and 2018 occurred and the overall aquifer yield was recognized to slightly diminish over a similar time span. Rainfall showed significant stable isotopic variations on the (stable) isotopic signature, the heaviest values being measured in 2017. In addition, the tritium values determined at the summit of Mt. Amiata and related to the first three months of year 2018, were sensibly lower than those recorded in 2011. Isotopically, a good agreement between rainfall vs. groundwater system was observed, suggesting that the aquifer can be used as a proxy for local climate changes. Eventually, three main hydrogeological patterns within the shallow Mt. Amiata aquifer were suggested, each one characterized by short-, medium- or long-term travel times, respectively, and a novel equation for a local meteoric water line was computed. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) distribution in groundwater is an important tool for investigating water-rock interaction processes as REEs content in aqueous systems strongly depends on the degree of rock weathering. However, subsequent to REEs' dissolution from the aquifers rocks, REEs' removal from solution by sorption or coprecipitation can occur. In this work, the concentrations of dissolved REEs were determined in groundwater of Mount Vulture volcanic aquifer. Mt. Vulture is a Pleistocene composite volcano located at the easternmost border of the Apennine compressive front whose aquifer core is mainly composed of pyroclastic and subordinate lava flow of different permeability, which give rise to distinct aquifer layers. The collected water samples were cold and slightly acidic water with electrical conductivity (EC) that varies over a wide range of values; in addition, Eh and dissolved oxygen (DO) of groundwater were also measured. The water samples, due to the high variability of some physical-chemical parameters such as EC and DO, were the object of a cluster analysis, which showed the presence of two main subset having substantial differences in the measured parameters. Thus the dataset was divided into a high salinity subset (EC > 800 µs/cm) with low Eh and OD values and a low salinity subset (EC < 800 µs/cm) characterized by higher OD and Eh values. The concentration of dissolved REEs in groundwater fluctuates over several order of magnitude and shows a slightly positive correlation with water temperature and a slightly negative correlation with the dissolved oxygen (DO); relationships with EC, pH and Eh are not observed. The Post-Archean Australian Shales (PAAS) normalized pattern of the high salinity subset showed an important fractionation between LREE and HREE and moderate CeN* and EuN* anomaly. Instead, the low salinity subset showed a minor fractionation between LREE and HREE and an important EuN* anomaly compared to the previous group. The EuN* anomaly of the whole dataset is in a positive correlation with the Eh whereas the CeN* is in weak negative correlation. These preliminary results confirm the usefulness of REEs' distribution in groundwater for assess water-rock interaction processes. [ABSTRACT FROM AUTHOR]

This study explores the co-existence of arsenic and fluoride in a volcanic-sedimentary aquifer in central Italy, aiming at identifying the risk areas for human health and the most likely processes deductible at regional/groundwater body scale leading to the observed co-contamination in groundwater.The study area is located in Latium (Central Italy) where undersaturated alkali-potassic formations largely outcrop, belonging to three different volcanic apparatus of Plio-Pleistocene age.Geochemical data from groundwater at 398 wells or springs are analyzed through statistical methods including clustering/PCA and geostatistical analysis. 29% of the sampled groundwaters exceeds the drinking water standard for F (1.5 mg/L), while 55% exceeds that for As (10.0 µg/L). Multivariate statistics suggest a widespread process of water-rock interaction with the K-alkaline volcanic formations releasing As, F, K, Si, V, Rb and PO4 to the groundwater. As and F show a good correlation (Pearson's r = 0.61) and define a separate component, suggesting that their background in groundwater might be governed by a common process.While in the peripheral areas of the volcanic districts, dominated by sedimentary deposits, the As-F correlation index does not present important fluctuations, Indicator Kriging shows specific As or F anomalies within the volcanic groundwater bodies and along the Tyrrhenian coastline. These anomalies seem to correspond to the zones with the highest thermal flux and/or are located near important structural lineaments. Fluoride anomalies close to mining sites (fluorite) have also been observed. We hypothesize that, unlike the regional co-contamination, these local anomalies are related to the upwelling of geothermal fluids along fracture/fault systems that mix with cold groundwater, or to the interaction with mineral deposits particularly enriched of these elements. [ABSTRACT FROM AUTHOR]

Diffuse nitrate pollution in groundwater is currently considered one of the major causes of water quality degradation. The use of stable isotope of nitrate can be a very useful tool in the investigation of diffuse contamination sources. Many nitrate sources can introduce nitrate in groundwater system, and among them sewage, animal manure, chemical fertilizer and natural soil mineralization. To discriminate between them is not simple but extremely useful, especially to implement management actions for groundwater protection.In this research the isotopic composition of nitrate was used to evaluate nitrate contamination sources and to identify geochemical processes occurring in two different hydrogeological environment: an alluvial aquifer in the western Piedmont Plain (NW Italy) and an alluvial-pyroclastic aquifer of the Campanian plain (S Italy).The analysed Piedmont plain is essentially an agricultural zone with cereals and forages cultivations, in which livestock farming (especially cows and pigs) are highly developed. Moreover, in the small towns domestic waste water is locally not connected to sewerage.In the studied Campanian plain, the land use shows a strong agricultural development, mostly in association to the numerous livestock activities (predominantly buffalo farming companies). The urbanized environment represents a relevant percentage of the area (about 8%) and extends mainly along the coast. Moreover, in some areas illegal building developments are present with illicit sewage connections or on-site sewage disposal.In both study areas, different sampling campaigns were performed to identify the nitrate distribution in groundwater. Groundwater samples were also collected for isotopic analysis (δ15N and δ18O) of dissolved nitrates.Both areas are characterized by high nitrate levels in groundwater, up to 180 mg/L. Isotope data of nitrate indicate that nitrate contamination in the Piedmont Plain originates from mixtures of synthetic fertilizers, manure and septic tank effluents. A further discrimination, made using boron isotopes, confirms that both domestic sewage and animal manure contributes to the nitrate contamination. At last, a significant denitrification process was highlighted especially in the shallow aquifer of Poirino Plateau, that is the most contaminated part of the study area.The source of nitrate in Campanian plain seems prevalently due to the spreading manure application to crops and to the urban sewage leakage. Indeed, this hypothesis seems confirmed by the changes in land use showing an increase of peri-urban areas, often not connected to the sewer systems.Determining the sources, distribution and persistence of nitrate in groundwater is a significant first step for a better management of water quality. Especially, we would propose the application of isotope techniques in both areas as an important support to face the attenuation in nitrate content. [ABSTRACT FROM AUTHOR]

In densely urbanized areas groundwater represents a valuable resource for the public, agricultural and industrial supply and, thus, for the socio-economic development. In this context, the high presence of anthropogenic activities together with the use of inadequate groundwater protection measures have a severe impact on the qualitative status of water bodies. Pollution in urban groundwater is caused by various sources including point sources commonly related to landfills and industrial spillages and responsible, for example, for chlorinated solvents and chromium contamination. To cope with this problem, statistical methods can be considered effective tools to provide key information for environmental planning and management. Among the various techniques, the Weights of Evidence (WofE) has proved to be a reliable method to assess the qualitative deterioration of the unconfined shallow aquifer due to non-point sources, typically related to nitrate contamination. This study provides the first application of the WofE methodology for estimating the susceptibility of both unconfined shallow and confined deep aquifers due to point source pollutants, as PCE+TCE and chromium, in the Province of Milan (northern Italy). The advantage of this technique consists in the possibility of identifying, for each pollutant, the hydrogeological and land use conditions that contribute to the development of contamination phenomena. This result is achieved by quantitatively evaluating the spatial correlation between pollutants occurrence and natural and anthropogenic factors potentially influencing the contamination in each aquifer.For the shallow aquifer analyses, the selected factors include: i) groundwater depth, ii) hydraulic conductivity of the unsaturated zone, iii) groundwater velocity, iv) degree of confinement and v) the distribution of industrial, artisanal and commercial settlements, representing potential sources of PCE+TCE and chromium contaminations. For the deep aquifer analyses, we selected: i) thickness of the fine sediments between shallow and deep aquifers, ii) distribution of pollutant concentrations in the shallow aquifer and iii) potential leakages from the shallow aquifer system to the deep one represented by the presence of wells screened in both aquifers (multi-aquifer wells). Results show that geological, hydrogeological and anthropogenic conditions influence the contamination of the shallow aquifer as expected in groundwater susceptibility studies. Moreover, results highlight that the shallow aquifer can easily represent a secondary source of contamination for the deep aquifer due to local heterogeneities of the fine sediments and the inappropriate design of multi-aquifer wells. All the investigated variables are combined to generate the aquifer susceptibility maps for the shallow and deep aquifers to PCE+TCE and chromium pollutions. These maps are a reliable support tool to be used by stakeholders and decision makers for an appropriate management and protection of the groundwater resource. [ABSTRACT FROM AUTHOR]

Excess of arsenic in groundwater is a worldwide problem threatening the health of the millions of people directly exposed to As-rich water intake. The problem is particularly acute in naturally occurring unconsolidated aquifers where As-rich groundwater is an easily accessible resource of drinking water, such as in India, Bangladesh and Vietnam. Naturally occurring high concentrations of As in groundwater also notoriously mark the Venetian Alluvial Plain (VAP) in Italy, affecting in particular the shallower aquifers. The VAP is characterized by a patchy As distribution with variable extensions and concentrations. Although empirical evidences exist about the relationship between As occurrence and other factors, several aspects regarding the physical and geochemical processes controlling As in the VAP aquifers remain unclear. This study aims to elucidate the geochemical conditions that control As mobilization in the VAP, in order to improve the knowledge about As-controlling processes in the study area and use them as a proxy to evaluate occurrence of As in other world regions characterized by a similar hydrogeological and geochemical settings, such as the Bengal Delta Plain. To this end, we focused in detail on an agricultural zone nearby the Venice lagoon, affected by As contamination (called "Aree Agricole West", AAW). The available data, collected by several hydrogeological surveys, show a spatial and temporal variability of As concentration, which can be associated to a variety of hydro-geochemical processes such as redox variations, sorption or reductive dissolution of As-rich iron oxy-hydroxides. In order to point out the consistency and the importance of these processes, we combined an advance exploration analysis with a PHREEQC 0D reactive model. The former part, performed by mean of Self-Organized Maps (SOM) algorithm, allows for identification of the main geochemical relationships within the study aquifer and the associated geochemical processes. The latter, instead, allows us for testing whether the supposed processes are able to fit the geochemical conditions of the study system. The results highlighted a strong effect of oxy-reductive potential on arsenic mobility, and it seems to be strictly correlated to organic matter degradation. The uprising of reduced condition, then, affects other mechanism such as reductive dissolution of iron hydroxides, ion exchange and sorption processes, causing arsenic mobilization. Moreover, this study shaded light on the existence of oxygen ingress as function of local water recharge events, which seems to be responsible of space/time redox variation. Thanks to the 0D model, it was possible to explain, in a semi-quantitative way, the effect of the oxygen ingress on the redox aquifer condition, and so to explain the arsenic variation. This study has to be intended as a first step toward a more detailed study, which will account for a 2D/3D reactive transport model aiming at elucidating arsenic mobility, including influence of recharge due to agricultural activities. [ABSTRACT FROM AUTHOR]