Marco Petitta

Nitrate source and fate at the catchment scale of the Vibrata River and aquifer (central Italy): an analysis by integrating component approaches and nitrogen isotopes

The aim of this study is to apply an integrated approach to determine nitrate sources and fate in the alluvial aquifer of the River Vibrata (Abruzzi, central Italy) by coupling the Isotope and the Component approaches. Collected data include concentration and nitrogen isotope composition of groundwater samples from the alluvial aquifer and nitrogen loads arising from agricultural and non-agricultural sources. The adopted methodology identified synthetic fertilizers as main sources of nitrate in the Vibrata alluvial aquifer. At the catchment scale, two different zones have been identified: the Upper Valley, where infiltration to groundwater is dominant and nitrogen easily migrates into the aquifer; in this area, nitrate content in groundwater is stable and normally higher than EU requirements. Moreover, streamwaters are fed by groundwater with a nitrate content likely lowered by denitrification processes occurring in the hyporheic zone. In the Lower Valley, runoff processes dominate and the nitrate content in surface waters is higher. Nevertheless, groundwater is locally affected by denitrification that breaks down the nitrate content, which often reaches values consistent with law limits.

Human alteration of groundwater–surface water interactions (Sagittario River, Central Italy): implication for flow regime, contaminant fate and invertebrate response

Many rivers worldwide are undergoing severe man-induced alterations which are reflected also in changes of the degree of connectivity between surface waters and groundwater. Pollution, irrigation withdrawal, alteration of freshwater flows, road construction, surface water diversion, soil erosion in agriculture, deforestation and dam building have led to some irreversible species losses and severe changes in community composition of freshwater ecosystems. Taking into account the impact of damming and flow diversion on natural river discharge, the present study is aimed at (i) evaluating the effects of anthropogenic changes on groundwater/surface water interactions; (ii) analyzing the fate of nitrogenous pollutants at the floodplain scale; and (iii) describing the overall response of invertebrate assemblages to such changes. Hydrogeological, geochemical and isotopic data revealed short- and long-term changes in hydrology, allowing the assessment of the hydrogeological setting and the evaluation of potential contamination by nitrogen compounds. Water isotopes allowed distinguishing a shallow aquifer locally fed by zenithal recharge and river losses, and a deeper aquifer/aquitard system fed by surrounding carbonate aquifers. This system was found to retain ammonium and, through the shallow aquifer, release it in surface running waters via the hyporheic zone of the riverbed. All these factors influence river ecosystem health. As many environmental drivers entered in action offering a multiple-component artificial environment, a clear relationship between river flow alteration and benthic and hyporheic invertebrate diversity was not found, being species response driven by the combination of three main stressors: ammonium pollution, man-induced changes in river morphology and altered discharge regime.

Correlation between groundwater flow and deformation in the fractured carbonate Gran Sasso aquifer (INFN underground laboratories, central Italy)

The Gran Sasso massif is a carbonate fractured aquifer with a spring discharge of more than 18 m3 s−1. The water table has been partially drained by two motorway tunnels and an underground laboratory (UL), located into the core aquifer. Karst features have limited role below the water table, where groundwater flow is mainly regulated by the fracture network. Two paired laser extensometers (BA and BC) recorded ground deformation in the UL. Changes in deformation correlate with the seasonal recharge/discharge cycle of groundwater flow and its long-term changes. Hydrostatic conditions prevail during the recharge phases because of the low permeability of local fractures, favoring compression, and hydraulic gradient increase above the UL. Fast groundwater flow through the high-permeability fault outcropping in the UL can enhance local dilatation for short periods. Spring discharge during exhaustion periods is fed by the low-permeability fracture network, fostering hydrodynamic conditions by hydraulic gradient decrease, diminishing compression and consequently favoring dilatation. Independent support to this conceptual model comes from local tests and a numerical model which highlights the hydromechanical strain effects induced by the hydrological cycle on the jointed rock mass along BA and the role of the hydraulic gradient on the rock mass deformation.

Long-term spatio-temporal hydrochemical and 222Rn tracing to investigate groundwater flow and water–rock interaction in the Gran Sasso (central Italy) carbonate aquifer

In the Gran Sasso fissured carbonate aquifer (central Italy), a long-term (2001–2007) spatio-temporal hydrochemical and 222Rn tracing survey was performed with the goal to investigate groundwater flow and water–rock interaction. Analyses of the physico-chemical parameters, and comparisons of multichemical and characteristic ratios in space and time, and subsequent statistical analyses, permitted a characterisation of the hydrogeology. At the regional scale, groundwater flows from recharge areas to the springs located at the aquifer boundaries, with a gradual increase of mineralisation and temperature along its flowpaths. However, the parameters of each group of springs may significantly deviate from the regional trend owing to fast flows and to the geological setting of the discharge spring areas, as corroborated by statistical data. Along regional flowpaths, the effects of seasonal recharge and lowering of the water table clearly cause changes in ion concentrations over time. This conceptual model was validated by an analysis of the 222Rn content in groundwater. 222Rn content, for which temporal variability depends on seasonal fluctuations of the water table, local lithology and the fracture network at the spring discharge areas, was considered as a tracer of the final stages of groundwater flowpaths.RésuméDans l’aquifère carbonaté fissuré du Grand Sasso (Italie centrale), une étude spatio-temporelle longue durée (2001–2007) par traçage hydrochimique incluant 222Rn a été réalisée dans le but d’étudier l’écoulement souterrain et l’interaction eau–roche. Des analyses des paramètres hydrochimiques, des comparaisons de ratios multiparamétriques caractéristiques dans l’espace et le temps et les analyses statistiques subséquentes ont permis une caractérisation de l’hydrogéologie. A l’échelle régionale, l’écoulement de l’eau souterraine depuis les aires de recharge jusqu’aux sources situées en limite de l’aquifère, s’accompagne d’une augmentation graduelle de la minéralisation et de la température le long du chenal d’écoulement. Toutefois, les paramètres de chaque groupe de sources peuvent s’écarter de façon significative de la tendance régionale, écarts dus à des écoulements rapides et aux caractéristiques géologiques des aires de décharge des sources, comme corroboré par les données statistiques. Le long des chenaux régionaux, les effets de la recharge saisonnière et les abaissements de la surface libre de la nappe causent clairement des changements des concentrations ioniques dans le temps. Ce modèle conceptuel a été validé par une analyse de la teneur en 222Rn dans l’eau de nappe. La teneur en 222Rn, dont la variabilité dans le temps dépend des fluctuations saisonnières de la nappe, la lithologie locale et le réseau de fractures des aires de décharge de l’aquifère, ont été considérés comme marqueurs des étapes finales des écoulements souterrains.ResumenSe llevó a cabo la traza hidroquímica espacio temporal a largo plazo (2001–2007) y el relevamiento de trazadores de 222Rn con el objetivo de investigar el flujo de agua subterránea y la interacción agua–roca en el acuífero carbonático fisurado del Gran Sasso (Italia Central). Los análisis de parámetros físico-químicos, y las comparaciones de cocientes característicos y multiquímicas en espacio y tiempo, y los análisis estadísticos subsecuentes permitieron una caracterización de la hidrogeología. En la escala regional, el agua subterránea fluye desde las áreas de recarga hacia los manantiales localizados en los bordes del acuífero, con un incremento gradual de mineralización y temperatura a lo largo de sus trayectorias de flujo. Sin embargo, los parámetros de cada grupo de manantiales pueden desviarse significativamente de la tendencia regional debido al flujo rápido y a la configuración geológica de las áreas de descarga de los manantiales, como fue corroborado por datos estadísticos. A lo largo de las trayectorias de flujos regionales, los efectos de la recarga estacional y el descenso de los niveles freáticos causa claramente cambios en las concentraciones iónicas a través del tiempo. Este modelo conceptual fue validado con un análisis del contenido de 222Rn en aguas subterráneas. El contenido de 222Rn, cuya variabilidad temporal depende de las fluctuaciones estacionales del nivel freático, la litología local y las redes de fracturas en las áreas de descarga de los manantiales, fue considerado como un trazador de las etapas finales de las trayectorias del flujo de agua subterránea.ResumoNo aquífero fissurado carbonatado de Gran Sasso (Itália central) foi efetuado um estudo com traçadores hidroquímicos e de 222Rn no espaço-tempo e a longo prazo (2001–2007), com o objetivo de investigar o fluxo de água subterrânea e a interação água–rocha. Análises dos parâmetros físico-químicos e comparações das relações multiquímicas e caraterísticas no espaço e no tempo, e subsequentes análises estatísticas, permitiram a caraterização da hidrogeologia. À escala regional, a água subterrânea flui das áreas de recarga para as nascentes localizadas nas fronteiras do aquífero, com um incremento gradual na mineralização e na temperatura ao longo do percurso. No entanto, os parâmetros de cada grupo de nascentes podem desviar-se significativamente da tendência regional, devido a fluxos mais rápidos e ao ambiente geológico das áreas de descarga das nascentes, como corroborado por dados estatísticos. Ao longo dos percursos de fluxo regionais, os efeitos da recarga sazonal e do rebaixamento do nível freático causam claramente alterações nas concentrações iónicas ao longo do tempo. Este modelo concetual foi validado por análises do conteúdo de 222Rn na água subterrânea. O conteúdo de 222Rn, para o qual a variabilidade temporal depende das flutuações sazonais do nível freático, da litologia local e da rede de fraturas nas áreas de descarga, foi considerado como um traçador dos estágios finais dos percursos de fluxo de água subterrânea.

Assessing the Effect of Saltwater Intrusion on Petroleum Hydrocarbons Plumes Via Numerical Modelling

A contamination by petroleum hydrocarbons was detected in a sandy aquifer below a petrochemical plant in Southern Italy. The site is located near the coastline and bordered by canals which, together with pumping wells, control submarine groundwater discharge toward the sea and seawater intrusion (SWI) inland. In this study, a three-dimensional flow and transport model was developed using SEAWAT-4.0 to simulate the density-dependent groundwater flow system. Equivalent freshwater heads from 246 piezometers were employed to calibrate the flow simulation, while salinity in 193 piezometers was used to calibrate the conservative transport. A second dissolved species, total petroleum hydrocarbons (TPH), was included in the numerical model to simulate the plumes originating from light non-aqueous-phase liquid. A detailed field investigation was performed in order to determine the fate of dissolved hydrocarbons. Fifteen depth profiles obtained from multilevel samplers (MLS) were used to improve the conceptual model, originally built using a standard monitoring technique with integrated depth sampling (IDS) of salinity and TPH concentrations. The calibrated simulation emphasises that density-dependent flow has a great influence on the migration pattern of the hydrocarbons plume. This study confirms that calibration of density-dependent models in sites affected by SWI can be successfully reached only with MLS data, while standard IDS data can lead to misleading results. Thus, it is recommended to include MLS in the characterization protocols of contaminated sites affected by SWI, in order to properly manage environmental pollution problems of coastal zones.

Hydrogeochemical changes before and during the 2016 Amatrice-Norcia seismic sequence (central Italy)

Seismic precursors are an as yet unattained frontier in earthquake studies. With the aim of making a step towards this frontier, we present a hydrogeochemical dataset associated with the 2016 Amatrice-Norcia seismic sequence (central Apennines, Italy), developed from August 24th, with an Mw 6.0 event, and culminating on October 30th, with an Mw 6.5 mainshock. The seismic sequence occurred during a seasonal depletion of hydrostructures, and the four strongest earthquakes (Mw ≥ 5.5) generated an abrupt uplift of the water level, recorded up to 100 km away from the mainshock area. Monitoring a set of selected springs in the central Apennines, a few hydrogeochemical anomalies were observed months before the onset of the seismic swarm, including a variation of pH values and an increase of As, V, and Fe concentrations. Cr concentrations increased immediately after the onset of the seismic sequence. On November 2016, these elements recovered to their usual low concentrations. We interpret these geochemical anomalies as reliable seismic precursors for a dilational tectonic setting.

Assessing the impact of large-scale dewatering on fault-controlled aquifer systems: a case study in the Acque Albule basin (Tivoli, central Italy)

The development of large-scale bedrock quarry operations often requires high-volume and long-term groundwater extraction to maintain a sustainable working environment. These dewatering activities often influence groundwater levels and flow patterns regionally. In the present study, the influence of the dewatering of the travertine quarry operations near the city of Tivoli, Italy, are quantitatively investigated through an integrated analysis of field data and numerical modeling. Lowering of regional groundwater levels in the vicinity of the quarry has led to destructive land subsidence and alterations to the flow system sustaining a hot-spring area. The study employs a finite element numerical model (FEFLOW) to evaluate and quantify the impact of the extensive dewatering on fault-controlled regional groundwater flow in the Acque Albule basin. By incorporating the physical field data and historical hydrologic information, the numerical model was calibrated against three groundwater scenarios, reproducing the effects of different exploitation activities, coupled with natural changes over the course of the quarry operation. The results indicate that groundwater withdrawals by the mining industry and by “Terme di Roma” spa resulted in the cessation of flow from the primary thermal spring and a drop in the phreatic level in the area consequently affected by land subsidence.RésuméL’exploitation à grande échelle de carrières de pierres de taille nécessite souvent d’extraire un volume d’eau souterraine important sur le long terme, afin de fournir un environnement de travail stable. Ces activités de dénoyage influencent souvent les niveaux piézométriques ainsi que les caractéristiques des écoulements régionaux. Dans la présente étude, l’influence du dénoyage lors d’une exploitation de carrière de travertin, près de la ville de Tivoli, Italie, a été étudiée quantitativement par analyse de données de terrains et modélisation numérique. L’abaissement des niveaux piézométriques régionaux à proximité de la carrière a entraîné une subsidence de terrain destructrice et des altérations du système d’écoulement alimentant une zone de sources chaudes. L’étude emploie un modèle à éléments finis (FEFLOW) pour évaluer et quantifier l’impact du dénoyage important du flux de la nappe souterraine du bassin contrôlé par faille dans le bassin d’Acque Albule. En incorporant les paramètres physiques et l’information hydrologique historique, le modèle numérique a été calibré pour trois scénarios reproduisant les effets de différentes activités d’exploitation, couplés à des modifications normales du mode d’opération de la carrière. Les résultats montrent que les prélèvements d’eau souterraine par l’industrie extractive et par le “Terme di Roma” spa aboutissent à l’arrêt de l’écoulement de la source thermale primaire et à un abaissement du niveau piézométrique dans la zone par suite affectée par la subsidence.ResumenEl desarrollo de operaciones a gran escala de excavaciones de rocas de base a menudo requiere la extracción de grandes volúmenes de agua subterránea por largos plazos para mantener un ambiente de trabajo sustentable. Estas actividades de drenaje a menudo influyen en los niveles de agua subterránea y en los patrones de flujo regional. En el presente estudio, se investiga cuantitativamente la influencia del drenaje en las operaciones de excavaciones de travertino en las cercanías de la ciudad de Tivoli, Italia, a través de un análisis integrado de datos de campo y de modelados numéricos.El descenso de los niveles regionales de agua subterránea en las vecindades de las excavaciones ha provocado una subsidencia destructiva del terreno y alteraciones en el sistema de flujo que sustenta un área de manantiales termales. El estudio emplea un modelo numérico de elementos finitos (FEFLOW) para evaluar y cuantificar el impacto del drenaje extensivo en el flujo subterráneo regional controlado por fallas en la cuenca Acque Albule. Para la incorporación de los datos físicos de campo y la información hidrológica histórica, el modelo numérico fue calibrado con respecto de tres escenarios de agua subterránea, reproduciendo los efectos de las diferentes actividades de explotación, acoplados con cambios naturales sobre el curso de la operación de la excavación. Los resultados indican que la extracción de agua subterránea para la industria minera y para el spa “Terme di Roma” resultaron en la cese del flujo proveniente del manantial termal primario y una caída en el nivel freático en el área consecuentemente afectada por la subsidencia del terreno.摘要进行大型基岩采石作业往往需要大量和长期排除地下水来维持可持续的工作环境。这些抽水活动往往会影响区域地下水水位和地下水流动模式。在本次研究中,通过现场数据的综合分析和数值模拟对意大利帝沃利附近石灰华采石场抽水作业的影响进行了定量研究。降低采石场附近区域地下水位已导致破坏性的地面沉降,也改变了维持温泉区域的地下水流系统。本次研究采用有限元数值模型(FEFLOW)来评价和量化大量抽取地下水对Acque Albule盆地由断层控制的区域地下水流的影响。通过结合物理场数据和历史水文资料,根据三种不同的地下水开采方案对数值模型进行了校正,再现不同地下水开采活动的影响和在采石作业过程中的自然变化。研究结果表明,采矿业和Terme di Roma水疗中心大量抽取地下水造成主要温泉的地下水流的中断和受地面沉降影响的区域潜水位的下降。RiassuntoL’estrazione di materiali litoidi su larga scala spesso necessita di emungimenti consistenti e duraturi, per consentire le operazioni di coltivazione sotto falda. Tali attività possono determinare un generale abbassamento dei livelli piezometrici ed alterare il deflusso idrico sotterraneo a scala regionale. Nel presente studio viene proposta un’analisi dei dati di campo, integrata con una modellazione numerica, per quantificare l’effetto degli emungimenti delle cave di travertino prossime all’abitato di Tivoli (Italia). Gli abbassamenti dei livelli di falda regionale, osservati nelle aree di coltivazione del travertino, hanno innescato fenomeni di subsidenza e alterazioni del regime idraulico di sorgenti termali. L’indagine utilizza un modello numerico ad elementi finiti (FEFLOW) per valutare e quantificare l’impatto dei prelievi idrici sull’acquifero regionale, nel bacino delle Acque Albule, abbinato alla presenza di sistemi di faglie in grado di determinare direttrici di flusso preferenziali. Il modello e’ stato calibrato su tre scenari di impatto antropico, utilizzando dati di campo e informazioni storiche sull’idrologia dell’area, per simulare l’effetto dei prelievi idrici con l’evolversi delle condizioni ambientali. I prelievi idrici indotti dall’industria mineraria e dalle “Terme di Roma” hanno determinato la cessazione del deflusso idrico delle principali sorgenti termali e abbassamenti piezometrici nell’area interessata da fenomeni di subsidenza.ResumoO desenvolvimento de operações de extração de pedra a grande escala requere, frequentemente, a extração de grandes volumes de água subterrânea durante longos períodos, de modo a manter um ambiente de trabalho sustentável. Estas atividades de drenagem influenciam muitas vezes os níveis de água subterrânea e os padrões de fluxo à escala regional. Neste estudo investigou-se quantitativamente a influência da drenagem de travertino explorado numa pedreira, perto da cidade de Tivoli, Itália, através de uma análise integrada de dados de campo e modelação numérica. A descida dos níveis regionais de água subterrânea nas imediações da pedreira conduziu à subsidência destrutiva do terreno e induziu alterações no sistema de fluxo que alimenta uma área de nascentes termais. O estudo aplica um modelo numérico de elementos finitos (FEFLOW) para avaliar e quantificar o impacte da drenagem intensiva no fluxo subterrâneo regional, controlado por falhas, na bacia de Acque Albule. Através da incorporação de dados físicos de campo e de informação hidrológica histórica, o modelo numérico foi calibrado comparando três cenários de água subterrânea, reproduzindo os efeitos das diferentes atividades de exploração, tendo em conta as variações naturais que decorrem durante a operação da pedreira. Os resultados indicam que as extrações de água subterrânea pela indústria mineira e pelo estabelecimento termal “Terme di Roma” resultaram na cessação do fluxo da fonte termal primária e numa descida do nível freático na área consequentemente afetada pela subsidência do terreno.

Fate of arsenic, phosphate and ammonium plumes in a coastal aquifer affected by saltwater intrusion

A severe groundwater contamination with extensive plumes of arsenic, phosphate and ammonium was found in a coastal aquifer beneath a former fertilizer production plant. The implementation of an active groundwater remediation strategy, based on a comprehensive pump and treat scheme, now prevents the migration of the dissolved contaminants into the marine environment. However, due to the sites proximity to the coastline, a seawater wedge was induced by the pumping scheme. Additionally the groundwater flow and salinity patterns were also strongly affected by leakage from the sites sewer system and from a seawater-fed cooling canal. The objective of this study was to elucidate the fate of arsenic and its co-contaminants over the sites history under the complex, coupled hydrodynamic and geochemical conditions that prevail at the site. A detailed geochemical characterisation of samples from sediment cores and hydrochemical data provided valuable high-resolution information. The obtained data were used to develop various conceptual models and to constrain the development and calibration of a reactive transport model. The reactive transport simulations were performed for a sub-domain (two-dimensional transect) of an earlier developed three-dimensional flow and variable density solute transport model. The results suggest that in the upper sub-oxic zone the influx of oxygenated water promoted As attenuation via co-precipitation with Al and Fe oxides and copper hydroxides. In contrast, in the deeper aquifer zone, iron reduction, associated with the release of adsorbed As and the dissolution of As bearing phases, provided and still provides to date a persistent source for groundwater pollution. The presented monitoring and modelling approach could be broadly applied to coastal polluted sites by complex contaminant mixture containing As.

Occurrence of volatile organic compounds in shallow alluvial aquifers of a Mediterranean region: Baseline scenario and ecological implications

A regional survey of eight volatile organic compounds (VOCs), namely BTEX (benzene, toluene, ethylbenzene and p-xylene) and four chlorinated aliphatic hydrocarbons (CAHs: chloroform, 1,2-dichloroethane, trichloroethene and tetrachloroethene), was carried out at 174 sites, in 17 alluvial aquifers of Abruzzo, a Mediterranean region of southern Italy, from 2004 to 2009. Frequency of detection, concentration range, spatial distribution pattern, and temporal trend of contaminant concentration in each aquifer were analyzed as well as the relationships between VOC concentrations and the total amount of precipitation during the 90days preceding each sampling date. A review of published ecotoxicological data, providing an indication of the biological risk associated with the observed levels of VOC contamination, was presented and discussed. BTEX concentrations were under detection limits in all the investigated aquifers, indicating absence of contamination. In contrast, CAH contamination occurred in 14 out of 17 aquifers. The two most frequently detected compounds were chloroform and tetrachloroethene. No significant temporal trend was observed for chloroform and tetrachloroethene concentrations during the six years of observation, indicating the persistence of stable contaminations, except for some slightly decreasing trends observed in three out of 17 aquifers. In four aquifers chloroform and tetrachloroethene concentrations increased with precipitations in the preceding months. Spatial patterns of contamination differed among aquifers, indicating highly complex contaminant distributions at aquifer scale not related to single-plume geometries. Patterns of contamination by chloroform and tetrachloroethene in the most urbanized aquifers were likely associated with multiple sources of VOCs not clearly detectable at the scale used in this study. In five out of 17 aquifers, chloroform and tetrachloroethene co-occurred at concentrations that are lethal to groundwater-dwelling organisms under a short exposure period (four days). Future studies should therefore consider the possibility that in the other aquifers groundwater-dwelling organisms might be physiologically damaged by sublethal VOC concentrations.

Groundwater of Rome

ABSTRACT This paper describes the contents of the new Hydrogeological Map of the City of Rome (1:50,000 scale). The map extends to the entire municipality (1285 km2) and is based on both the most recent scientific studies on the groundwater field and new survey activities carried out in order to fill the data gaps in several areas of the examined territory. The map is the result of a combination of different urban groundwater expertise and Geographic Information System (GIS)-based mapping performed using the most recent available data and has been produced with the intention of furnishing the City of Rome with the most recent and updated information regarding groundwater.