Giorgio Pilla

The Uprising of Deep Saline Paleo-Waters into the Oltrepò Pavese Aquifer (Northern Italy): Application of Hydro-Chemical and Shallow Geophysical Surveys

The alluvial aquifer of the Oltrepo Pavese plain sector (Po Valley, Northern Italy) is naturally contaminated by Na–Cl paleo-waters, rising from the tertiary marine substratum and mixing with the shallow groundwater. This phenomenon is localised along a buried tectonic discontinuity known as Vogherese Fault. A hydro-chemical (sampling for chemical analysis, log of electrical conductivity and temperature, continuous monitoring system) and a geophysical (VLF-EM, 2D and 3D ERT surveys, resistivity profiling, resistivity depth soundings) study was carried out to investigate the phenomenon. The research highlighted a spot spatial distribution of the saline contamination, suggesting the existence of isolated plumes of saltwater within the aquifer and a temporal variability of groundwater’s salinity. These results allowed at formulating a conceptual model based on the regional hydraulic continuity between the fracture network of the aquifer in the Apennines mountain range and the porous aquifer in the Oltrepo Pavese plain. Severe recharge events in the Apennines could be able to activate a mass or pressure transfer from the fractured to the porous aquifer and to cause the uprising of deep paleo-waters into the alluvial aquifer.

Occurrence of Extended Spectrum β-Lactamases, KPC-Type, and MCR-1.2-Producing Enterobacteriaceae from Wells, River Water, and Wastewater Treatment Plants in Oltrepò Pavese Area, Northern Italy

To evaluate the water compartment antibiotic-resistance contamination rates, 11 wells, five streams, and four treatment plants located in the Oltrepò Pavese area were screened for the presence of third generation cephalosporins resistant Gram-negative bacteria. Enterobacteriaceae were also characterized for the Extended-Spectrum-β-Lactamases (ESBLs), carbapenemases, and mcr-1 genes presence. From December 2014 to November 2015, 246 water samples were filtered, plated on Plate Count Agar, MacConkey Agar, and MacConkey Agar with cefotaxime. Isolates were species identified using AutoSCAN-4-System and ESBLs, carbapenemases, and colistin resistance determinants were characterized by PCR, sequencing, and microarray. Plasmid conjugative transfer experiments, PCR-based Replicon typing, Pulsed-Field Gel Electrophoresis, Multi-Locus-Sequence-Typing, and in-silico plasmid characterization were performed. A total of 132 enterobacteria isolates grew on MacConkey agar with cefotaxime: 82 (62.1%) were obtained from streams, 41 (31.1%) from treatment plants, and 9 (6.8%) from wells. Thirty out of 132 (22.7%) isolates, mainly belonging to Escherichia coli (n = 15) species, showed a synergic effect with piperacillin-tazobactam. A single ESBL gene of blaCTX−M-type was identified in 19/30 isolates. In further two E. coli strains, a blaCTX−M−1 gene co-existed with a blaSHV-type ESBL determinant. A blaSHV−12 gene was detected in two isolates of E. coli (n = 1) and Klebsiella oxytoca (n = 1), while any ESBL determinant was ascertained in seven Yersinia enterocolitica strains. A blaDHA-type gene was detected in a cefoxitin resistant Y. enterocolitica from a stream. Interestingly, two Klebsiella pneumoniae strains of ST307 and ST258, collected from a well and a wastewater treatment plant, resulted KPC-2, and KPC-3 producers, respectively. Moreover, we report the first detection of mcr-1.2 ST10 E. coli on a conjugative IncX4 plasmid (33.303 bp in size) from a stream of Oltrepò Pavese (Northern Italy). Both ESBLs E. coli and ESBLs/carbapenemase-producing K. pneumoniae strains showed clonal heterogeneity by Pulsed-Field Gel Electrophoresis and Multi-Locus-Sequence-Typing. During one-year study and taking in account the whole Gram-negative bacterial population, an average percentage of cefotaxime resistance of 69, 32, and 10.3% has been obtained for the wastewater treatment plants, streams, and wells, respectively. These results, of concern for public health, highlight the need to improve hygienic measures to reduce the load of discharged bacteria with emerging resistance mechanisms.

Application of statistical classification methods for predicting the acceptability of well-water quality

The application of statistical classification methods is investigated—in comparison also to spatial interpolation methods—for predicting the acceptability of well-water quality in a situation where an effective quantitative model of the hydrogeological system under consideration cannot be developed. In the example area in northern Italy, in particular, the aquifer is locally affected by saline water and the concentration of chloride is the main indicator of both saltwater occurrence and groundwater quality. The goal is to predict if the chloride concentration in a water well will exceed the allowable concentration so that the water is unfit for the intended use. A statistical classification algorithm achieved the best predictive performances and the results of the study show that statistical classification methods provide further tools for dealing with groundwater quality problems concerning hydrogeological systems that are too difficult to describe analytically or to simulate effectively.RésuméL’application de méthodes de classification statistique est étudiée—en comparant également avec les méthodes d’interpolation spatiale—pour prédire l’acceptabilité de la qualité de l’eau issue de forages, dans une situation où un modèle quantitatif efficace d’un système hydrogéologique considéré ne peut être développé. Dans la zone prise en exemple, au nord de l’Italie, l’aquifère est. localement affecté par une eau saline, et la concentration en chlorures est. le principal indicateur de la présence d’eau salée et de la qualité des eaux souterraines. L’objectif est de prédire si la concentration en chlorures de l’eau issue d’un forage est supérieure à la valeur autorisée, de sorte que l’eau n’est pas conforme à l’usage souhaité. Un algorithme de classification statistique a permis d’obtenir les meilleures performances de prévision et les résultats de cette étude montrent que les méthodes de classification statistique fournissent des outils plus poussés pour appréhender les problèmes de qualité des eaux souterraines, pour les systèmes hydrogéologiques trop difficiles à décrire de manière analytique ou à simuler de manière efficace.ResumenSe investiga la aplicación de métodos de clasificación estadística, en comparación también con los métodos de interpolación espacial, para predecir la aceptabilidad de la calidad del agua de pozos en una situación donde no se puede desarrollar un modelo cuantitativo eficaz del sistema hidrogeológico considerado. En el área del ejemplo, en particular en el norte de Italia, el acuífero se ve afectado localmente por el agua salina y la concentración de cloruro es el principal indicador tanto de la ocurrencia de agua salada como de la calidad del agua subterránea. El objetivo es predecir si la concentración de cloruro en un pozo de agua excederá la concentración permitida de modo que el agua no sea apta para el uso previsto. Un algoritmo de clasificación estadística logró los mejores resultados predictivos y los resultados del estudio muestran que los métodos de clasificación estadística proporcionan más herramientas para tratar los problemas de calidad del agua subterránea en relación con sistemas hidrogeológicos que son demasiado difíciles de describir analíticamente o de simularlos eficazmente.摘要调查了统计分类方法的应用情况—还与空间插入方法进行了比较—以预测无法建立水文地质系统有效定量模型的情况下水井水质的可接受性。特别是在意大利北部的研究案例区,含水层局部受到咸水的影响,氯化物的含量是出现盐水和地下水水质的主要指示物。目的就是预测水井中的氯化物含量是否超过允许的含量而使水不能使用。统计分类算法预测结果最好,研究结果显示,统计分类方法为处理很难解析描述或有效模拟的水文地质系统地下水水质问题提供了进一步的工具。ResumoA utilização de métodos de classificação estatística é investigada—em comparação também aos métodos de interpolação espacial—para prever a aceitabilidade da qualidade de água de poços em uma situação onde um modelo quantitativo efetivo do sistema hidrogeológico sob consideração não pode ser desenvolvido. Na área piloto no norte da Itália, em particular, o aquífero é localmente afetado por água salina e a concentração de cloreto é o principal indicador de ocorrência de água salgada e qualidade das águas subterrâneas. O objetivo é prever se a concentração de cloreto em um poço de abastecimento excederá a concentração permitida, assim a água não se adequaria ao uso pretendido. Um algoritmo de classificação estatística alcançou os melhores desempenhos de previsão e os resultados do estudo demonstram que os métodos de classificação estatística fornecem ferramentas adicionais para lidar com os problemas da qualidade das águas subterrâneas no viés dos sistemas hidrogeológicos que são muito difíceis de se descrever analiticamente ou se simular efetivamente.

COMPARISON BETWEEN VLF-EM AND RESISTIVITY ANOMALIES ASSOCIATED WITH SALT PALEO-WATERS CONTAMINATIONS IN AN ALLUVIAL AQUIFER: THE SAN RE TEST SITE (NORTHERN ITALY)

The alluvial aquifer of the Oltrepo Pavese plain sector (Po Valley, Northern Italy) is contaminated by Na-Cl paleo-waters, rising from the tertiary substratum and mixing with the shallow groundwater. This phenomenon is localized along the Vogherese Fault, a buried tectonic discontinuity. Geophysical surveys were undertaken in two separate phases to map and characterize the contaminations. The first phase involved resistivity depth soundings undertaken along a cross section of the Vogherese Fault and VLF-EM surveys carried out over 150 km 2 for a rapid assessment of the distribution of saline waters, even where no wells for sampling are available. NE-SW trends of high conductivity anomalies were revealed. These trends can be correlated to the occurrence of the Vogherese Fault trace and secondary sub-parallel discontinuities along which paleo-waters uprise. San Re test site was chosen as representative of the entire study area to carry out a more detailed phase of investigations which included: four resistivity depth soundings, five 2D ERT surveys (470 m long) that were undertaken along an approximately 2600 m long profile crossing the fault zone and overlapping a significant length of VLF-EM surveys and a resistivity profiling; another ERT survey was undertaken at a transversal angle to the profile; four 3D ERT surveys and a short spread 2D ERT were undertaken to achieve a detailed investigation of the salt water plumes. The overlapping of different surveys allowed a comparison between electromagnetic and resistivity anomalies associated with the occurrence of saltwater contaminations. The detectability of VLF-EM and resistivity profiling surveys when identifying saltwater contaminations was defined through a comparison with the saltwater plumes imaging obtained by 2D and 3D ERTs. On a total of 14 saltwater contaminations (steeply-dipping and well coupled with the transmitter) with a length ranging between 8 and 195 m, 50 % have been detected as conductivity boundary, while 50 % as conductivity body by VLF-EM surveys.

Application of influence diagrams for well contamination risk management: a case study in the Po plain, northern Italy

The aquifer of the Oltrepò Pavese plain (northern Italy) is affected by paleo-saltwater intrusions that pose a contamination risk to water wells. The report first briefly describes how the presence of saline water can be predicted using geophysical investigations (electrical resistivity tomography or electromagnetic surveys) and a machine-learning tool specifically developed for the investigated area. Then, a probabilistic graphical model for addressing the risk of well contamination is presented. The model, a so-called ‘influence diagram’, allows researchers to compute the conditional probability that groundwater is unsuitable for use taking into account the results of the geophysical surveys, the predictions of the machine-learning software, the related uncertainties and the prior probability of contamination in different sectors of the plain. The model, in addition, allows for calculation and comparison of the expected utility of alternative decisions (drilling or not drilling the well, or using another water source). The model is designed for use in ordinary decision situations and, although conceived for a specific area, provides an example that may be adapted to other cases. Some adaptations and generalizations of the model are also discussed.ResumeL’aquifère de la plaine de l’Oltrepo Pavese (Italie du Nord) est. touché par des intrusions d’eaux salées anciennes qui présentent un risque de contamination pour les forages d’eau. L’article décrit d’abord brièvement comment la présence d’eau salée peut être appréhendée en recourant à des investigations géophysiques (tomographies de résistivité électrique ou levés éléctromagnétiques) et à un outil d’apprentissage automatique développé spécifiquement pour la zone étudiée. Puis, un modèle graphique probabiliste, mis en œuvre pour répondre au risque de contamination des forages, est. présenté. Le modèle, nommé “diagramme d’influence”, permet aux chercheurs de calculer la probabilité conditionnelle que l’eau souterraine soit impropre aux usages, en prenant en compte les résultats des levés géophysiques, les prévisions du logiciel d’apprentissage automatique, les incertitudes liées et la probabilité a priori d’une contamination de différents secteurs de la plaine. De plus, le modèle permet le calcul et la comparaison de l’utilité attendue de décisions alternatives (réalisation ou non d’un forage, ou utilisation d’une autre source d’approvisionnement en eau). Le modèle est. destiné à une utilisation dans des situations de décisions habituelles et, bien que conçu pour un secteur spécifique, il fournit un exemple qui pourrait être adapté à d’autres cas. Certaines adaptations et généralisations de ce modèle sont également discutées.ResumenEl acuífero de la llanura Oltrepò Pavese (norte de Italia) se ve afectado por intrusiones de agua paleo-salada que representan un riesgo de contaminación para los pozos de agua. El documento, en primer lugar, describe brevemente cómo se puede predecir la presencia de agua salina utilizando investigaciones geofísicas (tomografía de resistividad eléctrica o estudios electromagnéticos) y una herramienta de aprendizaje automático desarrollada específicamente para el área investigada. Luego, se presenta un modelo probabilístico gráfico para abordar el riesgo de contaminación del pozo. El modelo, denominado “diagrama de influencia”, permite a los investigadores calcular la probabilidad condicional de que las aguas subterráneas no sean adecuadas para su uso teniendo en cuenta los resultados de los estudios geofísicos, las predicciones del software de aprendizaje automático, las incertidumbres relacionadas y la probabilidad previa de contaminación en diferentes sectores de la llanura. El modelo, además, permite calcular y comparar la utilidad esperada de decisiones alternativas (perforar o no perforar el pozo, o usar otra fuente de agua). El modelo está diseñado para su uso en situaciones de decisión ordinaria y, aunque se concibió para un área específica, proporciona un ejemplo que puede adaptarse a otros casos. También se discuten algunas adaptaciones y generalizaciones del modelo.摘要(意大利)北部Oltrepò Pavese平原含水层受到古海水入侵的影响,古海水入侵给水井带来了污染风险。本文首先简要描述了利用地球物理调查(电阻率层析成像或者电磁勘查)及专门为调查区研发的机器学习工具怎样可以预测是否存在着海水。然后,论述了针对水井污染风险概率图解模型。所谓的“影响图解”模型可以使研究人员计算综合考虑地球物理勘查结果、机器学习软件的预测结果、相关不确定性及平原不同区域污染的先验概率而认为地下水不适合利用的条件概率。另外,模型还可以对供选择的决定(钻井或者不钻井,或者使用另一水源)的预期实用性进行计算和对比。模型为普通决策情况下使用而设计,尽管为特定区域而构思,但模型提供了可能适用于其它情况的例子。文章还论述了一些适应性和概括性。RiassuntoL’acquifero della pianura alluvionale dell’Oltrepò Pavese è interessato da un particolare fenomeno d’intrusione di paleo-acque a elevata salinità che determinano un rischio di contaminazione dei pozzi idrici da realizzare. Nell’articolo si descrive brevemente come la presenza di acque salate possa essere prevista sia mediante indagini geofisiche (tomografia elettrica o indagini elettromagnetiche) sia attraverso un algoritmo di machine learning specificamente sviluppato per l’area di indagine. Viene presentato, successivamente, un modello grafico-probabilistico per la gestione del rischio di contaminazione dei pozzi. Il modello, un “diagramma di influenza”, permette di calcolare la probabilità condizionale che l’acqua di falda non sia idonea all’uso considerando i risultati delle indagini geofisiche, le previsioni dell’algoritmo di machine learning, le relative incertezze e la probabilità a priori di contaminazione nei diversi settori della pianura. Il modello, infine, permette di calcolare e confrontare l’utilità attesa di decisioni alternative quali realizzare o non realizzare un pozzo oppure usare un’altra fonte di approvvigionamento idrico. Il modello è progettato per essere impiegato in situazioni ordinarie e, anche se sviluppato per un’area specifica, rappresenta uno strumento che può essere adattato ad altri contesti idrogeologici con presenza di contaminazione. Nell’articolo sono discusse, anche, alcune varianti ed. estensioni del modello messo a punto.ResumoO aquífero da planície de Oltrepò Pavese (norte da Itália) é afetado por intrusões de paleo-águas salinas que oferecem um risco de contaminação para poços de água. O artigo, primeiramente, descreve de forma breve como a presença de água salina pode ser estimada utilizando métodos de investigação geofísica (tais como tomografia de resistividade elétrica ou levantamentos eletromagnéticos) e uma ferramenta de aprendizado de máquina (inteligência artificial) desenvolvida especificamente para a área investigada. Com isso, o modelo gráfico de probabilidade para acessar os riscos de contaminação é apresentado. O modelo, chamado de “diagrama de influência”, permite que os pesquisadores calculem a probabilidade condicional de qual água subterrânea é imprópria para uso, levando em consideração os resultados dos levantamentos geofísicos, as estimativas do algoritmo de aprenziado de máquina, as incertezas relacionadas e a probabilidade de contaminação prévia de diferentes setores da planície. O modelo, em adição, permite que se calcule e compare a utilidade esperada de decisões alternativas (perfurar ou não perfurar um poço, ou utilizar outra fonte de água). O modelo é desenvolvido para uso em situações de tomadas de decisões comuns e apesar de ter sido concebido para uma área específica, apresenta um exemplo que talvez possa ser adaptado para outros casos. Algumas adaptações e generalizações do modelo também são discutidas.

A multidisciplinary study of Benetutti thermal waters (Tirso Valley, Sardinia)

We report a multidisciplinary study of Benetutti thermal waters based on hydrochemistry, isotopic techniques, structural geology and geophysical surveys. Seven thermal waters and two cold spring waters have been studied. Thermal waters show temperature values ranging between 28 °C and 42 °C, a medium mineralization and a sodium-chloride chemical hydrofacies. Isotopes of the water molecule allowed verifying that these waters have not been affected by isotopic exchange phenomena with the Sardinian granite complex aquifer. VLF-EM (Very Low Frequency-Electromagnetics) surveys were undertaken for a rapid assessment of the distribution of thermal waters over vast areas. A northeast-southwest trend of high conductivity anomalies was revealed. This trend can be correlated to the occurrence of sub-parallel discontinuities along which thermal waters uprise.