Francesco Zarlenga

A hydrogeological conceptual model of the Suio hydrothermal area (central Italy)

A hydrogeological conceptual model has been developed that describes the hydrothermal system of Suio Terme (central Italy). The studied area is located along the peri-Tyrrhenian zone of the central Apennines, between the Mesozoic and Cenozoic carbonate platform sequences of the Aurunci Mountains and the volcanic sequences of the Roccamonfina. A multi-disciplinary approach was followed, using new hydrogeological surveys, the interpretation of stratigraphic logs of boreholes and water wells, and geophysical data—seismic sections, shear-wave velocity (Vs) crustal model and gravimetric model. The collected information allowed for construction of a conceptual hydrogeological model and characterization of the hydrothermal system. The Suio hydrothermal system is strongly influenced by the Eastern Aurunci hydrostructure. Along the southeastern side, the top of the hydrostructure sinks to −1,000xa0m relative to sea level via a series of normal faults which give origin to the Garigliano graben. Geological and hydrogeological data strongly suggest the propagation and mixing of hot fluids, with cold waters coming from the shallow karst circuit. The aquitard distribution, the normal tectonic displacements and the fracturing of the karst hydrostructure strongly influence the hydrothermal basin. Carbon dioxide and other gasses play a key role in the whole circuit, facilitating the development of the hydrothermal system. The current level of knowledge suggests that the origin of the Suio hydrothermalism is the result of interaction between the carbonate reservoir of the Eastern Aurunci Mountains and the hot and deep crust of this peri-Tyrrhenian sector, where the Roccamonfina volcano represents the shallowest expression.RésuméUn modèle hydrogéologique conceptuel a été développé décrivant le système hydrothermal des Thermes de Suio (Centre de l’Italie). La zone étudiée est située le long de la zone péri-tyrrhénienne du centre des Apennins, entre les séquences de plateforme carbonatée mésozoïque et cénozoïque des Monts Aurunci et les séquences volcaniques de Roccamonfina. Une approche multi disciplinaire a été menée, en utilisant de nouvelles données hydrogéologiques, l’interprétation des logs stratigraphiques des forages et puits d’eau, et des données géophysiques—section sismiques, modèle de la croûte avec vitesse des ondes de cisaillement (Vs) et modèle gravimétrique. L’information collectée a permis d’établir un modèle conceptuel hydrogéologique et de caractériser le système hydrothermal. Le système hydrothermal de Suio est fortement influencé par l’hydrostructure d’Aurunci à l’Est. Le long du versant sud est, la partie sommitale de l’hydrostructure plonge à −1,000xa0m sous le niveau de la mer par l’intermédiaire de séries de failles normales qui sont à l’origine du graben de Garigliano. Les données géologiques et hydrogéologiques suggèrent fortement une propagation et un mélange de fluides thermaux avec des eaux froides circulant dans les conduits karstiques de faible profondeur. L’extension d’un aquitard, les déplacements tectoniques normaux et la fracturation de l’hydrostructure karstique influence de manière importante le bassin hydrothermal. Le gaz carbonique et les autres gaz jouent un rôle clef dans l’ensemble du circuit, facilitant le développement du système hydrothermal. Le niveau actuel de connaissance suggère que l’origine de l’hydrothermalisme de Suio est le résultat d’interactions entre le réservoir carbonaté des Monts Aurunci à l’Est et la croûte chaude et profonde de ce secteur péri-Tyrrhénien, où le volcan de Roccamonfina représente l’expression la plus superficielle.ResumenSe ha desarrollado un modelo hidrogeológico conceptual que describe el sistema hidrotermal de Suio Terme (Italia central). El área estudiada se localiza a lo largo de la zona peri-tirrénica de los Apeninos centrales, entre las secuencias de la plataforma carbonática del Mesozoico y Cenozoico de las montañas de Aurunci y las secuencias volcánicas de Roccamonfina. Se aplicó un enfoque multidisciplinario, utilizando nuevos relevamientos hidrogeológicos, interpretación de registros estratigráficos de perforaciones y de pozos de agua, y datos geofísicos—secciones sísmicas, modelo de corte transversal de la velocidad de onda de corte (Vs) y modelo gravimétrico. La información recogida permitió la construcción de un modelo hidrogeológico conceptual y la caracterización del sistema hidrotermal. El sistema hidrotermal de Suio está fuertemente influenciado por la hidroestructura de Aurunci Oriental. A lo largo del lado sureste, la parte superior de la hidrostructura se hunde a −1,000xa0m en relación con el nivel del mar a través de una serie de fallas normales que dan origen al graben Garigliano. Los datos geológicos e hidrogeológicos sugieren fuertemente la propagación y mezcla de fluidos calientes con aguas frías procedentes del circuito kárstico poco profundo. La distribución del acuitardo, los desplazamientos tectónicos normales y la fractura de la hidrostructura kárstica influyen fuertemente en la cuenca hidrotermal. El dióxido de carbono y otros gases desempeñan un papel clave en todo el circuito, facilitando el desarrollo del sistema hidrotermal. El nivel actual de conocimiento sugiere que el origen del hidrotermalismo de Suio es el resultado de la interacción entre el depósito carbonático de las montañas de Aurunci Oriental y la corteza caliente y profunda de este sector peri-Tirreno, donde el volcán Roccamonfina representa la expresión más superficial摘要建立了描述(意大利中部)Suio Terme水热系统的水文地质概念模型。研究区位于沿Aurunci山脉中生代和新生代碳酸盐平台序列与罗卡蒙菲纳火山序列之间的亚平宁山脉中部伊特鲁里亚周边地区。利用新的水文地质调查结果、钻孔和水井地层录井的解译以及地球物理资料 (地震剖面、剪切波速度(Vs)地壳模型和重力模型)采用了多学科的方法。收集到的信息可以建立一个概念水文地质模型以及能够描述水热系统的特征。Suio水热系统受到Aurunci东部水结构的强烈影响。沿东南面,水结沟顶部通过一系列正断层相对于海平面下沉了1,000米,这些正断层造就了加里利亚诺地堑。地质资料和水文地质资料清楚地表明了热液的传播及其和来自浅层岩溶通道的冷水的混合。弱透水层的分布、正向构造位移及岩溶水构造的断裂强烈影响水热盆地。二氧化碳和其它气体在这个通道中发挥着关键作用,促进了水热系统的发育。目前所掌握的情况表明,Suio水热作用是Aurunci山脉东部碳酸盐储和这个伊特鲁里亚区周边热的和深部地壳之间的相互作用造成的,在伊特鲁里亚周边地区,罗卡蒙菲纳火山代表着最浅的地壳。ResumoFoi desenvolvido um modelo hidrogeológico conceitual que descreve o sistema hidrotermal da Estância Termal de Suio (Itália Central). A área estudada está localizada ao longo da zona peri-Tirrena dos Apeninos centrais, entre as sequências da plataforma carbonática Mesozoica e Cenozoica das Montanhas Aurunci e sequências vulcânicas da Roccamonfina. Uma abordagem multidisciplinar foi seguida usando novas pesquisas hidrogeológicas, a interpretação de registros estratigráficos de perfurações, poços de água e dados geofísicos—seções sísmicas, modelo de crosta da velocidade de onda de cisalhamento (Vs) e modelo gravimétrico. A informação coletada permitiu a construção de um modelo hidrogeológico conceitual e a caracterização do sistema hidrotermal. O sistema hidrotermal de Suio é fortemente influenciado pela hidroestrutura Oriental do Aurunci. Ao longo da área sudeste, o topo da hidroestrutura rebaixa a − 1,000xa0m em relação ao nível do mar através de uma série de falhas normais que dão origem ao graben Garigliano. Dados geológicos e hidrogeológicos sugerem fortemente a propagação e mistura de fluidos quentes com água fria proveniente do circuito cárstico raso. A distribuição do aquitardo, os deslocamentos tectônicos normais e a fratura da estrutura cárstica influenciam fortemente a bacia hidrotermal. Dióxido de carbono e outros gases desempenham papel fundamental em todo circuito, facilitando o desenvolvimento do sistema hidrotermal. O nível atual de conhecimento sugere que a origem do hidrotermalismo de Suio é o resultado da interação ente o reservatório carbonático e as Montanhas Oridentais Aurunci e a crosta quente e profunda deste setor peri-Tirreno, onde o vulcão Roccamonfina representa a manifestação mais superficial.

Hydrogeological study and numerical model of the Suio-Castelforte hydrothermal area (central Italy)

A numerical simulation has been performed through the natural geothermal system of Suio-Castelforte (LT) in order to investigate the hydothermal area and assess its geothermal potentiality. Starting from geological and hydrogeological data a 2D conceptual model has been built. For numerical purpose, the latter idealizes and simplifies the natural system. The area has been affected by a temperature gradient, from low to medium enthalpy, related to the Quaternary volcanism. By a FEM (Finite Element Model) method, using the COMSOL MULTIPHYSICS® software, a homogeneous and isotrope media have been assumed, simulating the groundwater flow and simultaneous heat transfer. Using the porous media approach, Darcy and heat transfer laws have been applied in steady-state conditions. The results have been compared with the collected data and bibliography.

A hydrogeological study to assess the geothermal potentiality of Suio Terme (central Italy)

The study concerns part of the plain sector of Aosta Valley (NW Italy). The investigated area is located between the cities of Sarre-Gressan and Pollein-Saint Christophe and is characterized by the presence of hexavalent chromium in the main shallow unconfined aquifer. The pollution is probably related to the negative environmental effects induced by the industrial steel production that since 1915 is present over the area. Since 1990 the industrial area was subjected to a number of direct investigations aimed to assess the contamination intensity. A preliminary remediation activity has been developed in last decades but the contaminants have been still observed in the groundwater monitoring network. This study highlights the set-up of a groundwater conceptual and numerical model of the shallow aquifer aimed to better understand and analyze the transport dynamics of hexavalent chromium in the local aquifer. The simulation is performed using the specific finite element software Feflow for groundwater flow and mass transport modeling. The hydrogeological setting of this area is related to the different sedimentary glacial, lacustrine and fluvial processes which characterized the bottom of the Aosta valley during the Quaternary. The shallow 80m-width aquifer is constituted by sandy to gravelly deposits and presents rare silty lens while its bottom is characterized by a decametric lacustrine silty level. The main aims of the numerical model are to give a more unequivocal explanation of the origin of the contamination and to support the predictive analyses in order to design an efficient site remediation for soil and groundwater. This represents a fundamental task in order to preserve the safety of the public water uses supplied by the aquifer. The preliminary hypothesis about the source of contaminations are still uncertain and referred to different scenarios that have to be further investigated by comparing monitoring data and transient flow simulation conditions.GroundWater Heat Pump (GWHP) technology has experienced increased implementation throughout several parts of the world. Water is discharged into an aquifer for cooling and heating buildings, which has the potential to cause significant environmental impacts associated with groundwater thermal interference. The TAZ is a thermal plume of colder or warmer re-injected groundwater resulting from the common use of well-doublets for groundwater-sourced heating or cooling. Plume propagation occurs primarily through advection, and tends to degrade following moving water. Plumes are considered a potential anthropogenic geothermal resource or pollution, depending on downstream aquifer usage (thermal feedback). These risks increase in densely urbanized areas. In fact, where depth to groundwater at a site is very low rising-up of discharged water along the well column could be very dangerous, rendering the dispersion system ineffective, and potentially causing damage to existing buildings and infrastructures in the surrounding area. Moreover, in terms of re-injection after a GWHP plant, increased contact surface between the disperser and the aquifer has other potential heat dissipation benefits. The objectives of this study were to investigate alternatives to traditional drilled wells for re-injection and dispersion of water in aquifers downstream of GWHP systems. In particular, we evaluated by the modeling simulations, the potential for reverse use of commercial gabion draining in various types of ground configuration and interconnection with prefabricated vertical drain systems. The modeling results showed the use of gabiondrains instead of reinjection wells tended to develop a TAZ, which primarily effected the surficial portion of the aquifer. TAZ development served an important role in decreasing thermal feedback risks, and reduced the relative distance between abstraction and re-injection in well-doublet schemes.