Alberto Tazioli

A DNA tracer used in column tests for hydrogeology applications

Tracing techniques are commonly used to investigate groundwater quality and dynamics, as well as to measure the hydrogeological parameters of aquifers. The last decade has seen a growing interest in environmentally friendly tracers, including single-stranded DNA molecules. In this study, an electrolytic tracer and a synthetic DNA tracer are comparatively evaluated in laboratory scale tests to assess their potential application in field studies aimed at investigating groundwater environments. A real-time quantitative Polymerase Chain Reaction assay was developed and optimized to detect and quantify the DNA tracer, while tracer column tests were performed to investigate the DNA tracer behavior and to compare it to the electrolytic tracer. The results show that the DNA tracer has an almost pure convective flow, while the KCl tracer experiences dispersive behavior. The tracing method proposed can be applied in hydrogeological field studies involving calcareous fractured rock systems, with the DNA tracer particularly suitable in tracing karst systems, which are often characterized by several conduits of flow. To test the DNA tracer in operation, a preliminary test was conducted in the field.

Characterizing the Recharge of Fractured Aquifers: A Case Study in a Flysch Rock Mass of the Northern Apennines (Italy)

12 springs from the northern Apennines of Italy were studied by means of a comprehensive hydrogeological investigation to unravel recharge processes taking place in a highly fractured slab of flysch rock hosting the corresponding aquifers. Several campaigns were carried out during the period 2005–2008 to gather springs’ discharge together with electrical conductivity and temperature data. Water samples were collected and allowed the determination of the major ions (Ca2+, Mg2+, Na+, K+, SO4 2−, HCO3 −, Cl−) and the isotopic content (δ18O). Additionally, groundwater discharge from 3 selected springs was measured continuously using pressure-transducers. Over the same period, reference δ18O values for rainfall and snow-melt water were collected monthly by a rain-gauge. Results highlighted an aquifer-like behavior of this slab of flysch rock. The springs are characterized by a Ca–HCO3 hydro-facies and an increase of groundwater mineralization has been noticed moving toward the base of the slab; the mean discharges are between 0.3 and 0.7 l·s−1 and suffered a marked variability during the year; the total maximum yield is about 155,000 m3 while the total discharge volume is around 320,000 m3·y−1. By processing the δ18O isotope values from springs (mean annual values ranged from −9.67 and −10.42 ‰) and by combining them with rainfalls datasets, results show that the main aliquot of recharge occurs in the winter—spring months and it is principally related to the solid precipitations (snow-melt).

The Mt Conero limestone ridge: the contribution of stable isotopes to the identification of the recharge area of aquifers

The recharge settings of aquifers (as those of the carbonate ridges in central Apennines) is strongly dependent on hydrogeological and geo-structural complexity; in fact, geochemical data, hydrographs interpretation, hydrogeological and geo-structural surveys, tracer and isotope data are usually not so developed and quite difficult to put into relation each other. In this paper, the importance of relating isotope techniques to hydrogeological survey on the recharge area evaluation is demonstrated by studying the system of the Mt Conero limestone ridge, located in central Italy close to the Adriatic sea. A closed system, at a pilot scale, with sufficiently well defined outcropping areas of aquifer, which is offering a contribution to the aquifer recharge area evaluation. In this study a hydrogeological investigation was performed to identify the infiltration areas in the aquifer, analysing the entire geological formation divided into several members, each of them showing different hydrogeological behaviour. In addition, periodic sampling of groundwater and of precipitation at different elevations were carried out to study the isotopic composition over a period of about 4 years. Weighted mean and arithmetic mean of isotopes were used in the gradient calculation and compared giving actually different results. The mean recharge altitude of the aquifer, as evaluated by weighted mean of isotopes, is about 100 m higher than the average elevation of the aquifer outcrop; moreover, it was proven that the vast majority of the recharge is due to the more permeable members of the aquifer (about 20% of the outcropping rocks, located at higher elevation). The recharge mechanism of the aquifer is therefore depending both on the isotope values of the local precipitation and on the distinct infiltration conditions existing in the lithotypes.

DNA and fluorescein tracer tests to study the recharge, groundwater flowpath and hydraulic contact of aquifers in the Umbria-Marche limestone ridge (central Apennines, Italy)

The purpose of this paper is to highlight the hydrogeological contact among aquifers in karst and fissured systems and study the different flowpaths present in said aquifers; given the complex hydrogeological and tectonics settings, detailed surveys in the Umbria-Marche limestone ridges and tracer field tests were used to achieve this goal. DNA and fluorescent tracers were injected into a sinkhole and thereafter recovered at different points, allowing both for the identification of contact among aquifers, as well as the main and secondary directions of groundwater. The tracer tests have shown that the majority of the groundwater flow is directed towards the axis of the tectonic structures, emerging in more depressed areas. In addition, they have confirmed the influence of karstification on the recharge, which allows for a more detailed characterisation of water circulation in the unsaturated zone of the Maiolica and the Calcare Massiccio limestone aquifers thus offering confirmation of the hydrogeological survey results, and providing additional information that was previously unknown. Furthermore, the DNA tracer provided good results in the field especially in the karst systems and fissured rocks, thus confirming its appropriacy for flowpath investigations and vulnerability analyses of springs. In particular, DNA is suitable for very large amounts of groundwater owing to its very low detection limit. Further investigations and studies are, however, required to assess its validity also for the evaluation of hydrogeological parameters.

Hydrogeological and geochemical characterisation of the Rock of Orvieto

The town of Orvieto, located on the Rock of the same name, is an example of “vulnerable town”; problems of slope instability connected with the lithological and morphological characteristics of the Rock have been thoroughly examined and discussed during previous research studies. Hydrogeochemical data about groundwater recharging the springs present in the area were never taken into account. Pollution of the springs is well known but still occurs for unclear reasons. The aim of this work is therefore to present the results of a hydrogeological and geochemical investigation of all the springs along the slopes of Orvieto hill and at the foot of the tuffaceous Rock, to characterize the groundwater flow paths and to suggest a possible source of contamination. The research study was carried out during three hydrogeochemical surveys in the years 1998–1999, 2003–2004, and 2007–2008.

Natural Hazard Analysis in the Aspio Equipped Basin

The purpose of this paper is to study floods, groundwater pollution and landslides in a small watershed characterized by high hydrogeological hazard, high population density and widespread industrial and commercial settlements. Measurements were performed to study hydrogeological hazard in the watershed during 2011, 2012 and 2013. First the relation between groundwater and surface water was estimated; second, the rainfall-runoff relationship was assessed. Some rainfall events were analysed to investigate the watershed behaviour in different periods over the hydrologic year. The analysis stressed the importance of the rainfall events, soil moisture and hydrological conditions. From this study it’s apparent that the natural hazard (i.e. floods, landslides and pollution hazard) can be better individuated and predicted in a small basin rather than in a wider one. Furthermore, these studies can be easily implemented in other basins with similar features in all the northern Mediterranean area.

Chemical and isotopic investigations (δ18O, δ2H, 3H, 87Sr/86Sr) to define groundwater processes occurring in a deep-seated landslide in flysch

Deep-seated landslides are complex systems. In many cases, multidisciplinary studies are necessary to unravel the key hydrological features that can influence their evolution in space and time. The deep-seated Berceto landslide, in the northern Apennines of Italy, has been investigated in order to define the origin and geochemical evolution of groundwater (GW), to identify the slope system hydrological boundary, and to highlight the GW flow paths, transit time and transfer modalities inside the landslide body. This research is based on a multidisciplinary approach that involves monitoring GW levels, obtaining analyses of water chemistry and stable and unstable isotopes (δ18O-δ2H, 3H, 87Sr/86Sr), performing soil leaching tests, geochemical modelling (PHREEQC), and principal component analysis (PCA). The results of δ18O-δ2H and 87Sr/86Sr analyses show that the source of GW recharge in the Berceto landslide is local rainwater, and external contributions from a local stream can be excluded. In the landslide body, two GW hydrotypes (Ca-HCO3 and Na-HCO3) are identified, and the results of PHREEQC and PCA confirm that the chemical features of the GW depend on water–rock interaction processes occurring inside the landslide. The 3H content suggests a recent origin for GW and appears to highlight mixing between shallow and deep GW aliquots. The 3H content and GW levels data confirm that shallow GW is mainly controlled by a mass transfer mechanism. The 3H analyses with GW levels also indicate that only deep GW is controlled by a pressure transfer mechanism, and this mechanism is likely the main influence on the landslide kinematics.RésuméLes glissements de terrain ancrés en profondeur sont des systèmes complexes. Dans de nombreux cas, des études pluridisciplinaires sont nécessaires pour mettre en évidence les principales caractéristiques hydrologiques qui peuvent influencer leur évolution spatio-temporelle. Le glissement de terrain ancré en profondeur de Berceto, dans le Nord des Apenins en Italie, a étudié afin de définir l’origine et l’évolution géochimique des eaux souterraines (ESO), d’identifier les limites hydrologiques du système, et de mettre en évidence les circulations d’ESO, le temps de transit et de transfert au sein du glissement de terrain. Cette recherche repose sur une approche pluridisciplinaire qui implique la surveillance des niveaux piézométriques, la réalisation d’analyses de la chimie de l’eau et des isotopes stables et instables (δ18O-δ2H, 3H, 87Sr/86Sr), de tests de lixiviation de sols, la modélisation géochimique (PHREEQC), et l’analyse en composantes principales (ACP). Les résultats des analyses de δ18O-δ2H et 87Sr/86Sr montrent que la recharge des ESO dans le glissement de terrain de Berceto a une origine associée aux précipitations locales, et que des contributions externes à partir d’un cours d’eau local peuvent être exclues. Au sein du glissement de terrain, deux types d’eaux souterraines (Ca-HCO3 et Na-HCO3) sont identifiés, et les résultats de PHREEQC et de l’ACP confirment que les caractéristiques chimiques des ESO sont marquées par les processus d’interaction eau roche qui prennent place dans le glissement de terrain. La concentration en 3H suggère une origine récente des ESO et semble mettre en évidence un mélange entre certaines ESO peu profondes et profondes. Les teneurs en 3H et les données piézométriques confirment que les ESO peu profondes sont principalement contrôlées par un mécanisme de transfert de masse. Les analyses d’3H combinées à celles des niveaux piézométriques indiquent également que seules les eaux souterraines profondes sont contrôlées par un mécanisme de transfert de pression, et que ce mécanisme est. probablement la principale influence sur la cinématique du glissement de terrain.ResumenLos deslizamientos profundos son sistemas complejos. En muchos casos, se necesitan estudios multidisciplinarios para desentrañar las principales características hidrológicas que pueden influir en su evolución en el espacio y el tiempo. Se investigó el deslizamiento profundo de Berceto, en los Apeninos septentrionales de Italia, para definir el origen y la evolución geoquímica del agua subterránea (GW), para identificar el límite hidrológico del sistema de taludes y resaltar las trayectorias de flujo del GW, el tiempo de tránsito y las modalidades de transferencia dentro del cuerpo del deslizamiento. Esta investigación se basa en un enfoque multidisciplinario que implica monitorear niveles de GW, obtener análisis de química del agua e isótopos estables e inestables (δ18O-δ2H, 3H, 87Sr/86Sr), realizar pruebas de lixiviación del suelo, modelado geoquímico (PHREEQC) y la componente principal de los análisis (PCA). Los resultados de los análisis de δ18O-δ2H and 87Sr/86Sr muestran que la fuente de recarga del GW en el deslizamiento de Berceto es el agua de la lluvia local, y se pueden excluir las contribuciones externas de un flujo local. En el cuerpo del deslizamiento, se identifican dos hidrotipos GW (Ca-HCO3 and Na-HCO3) y los resultados de PHREEQC y PCA confirman que las características químicas del GW dependen de los procesos de interacción agua–roca que ocurren dentro del deslizamiento. El contenido de 3H sugiere un origen reciente para el GW y parece resaltar la mezcla entre alícuotas de GW superficiales y profundas. El contenido de 3H y los datos de los niveles de GW confirman que el GW somera está controlado principalmente por un mecanismo de transferencia de masa. Los análisis de 3H con los niveles de GW también indican que solo el GW profundo está controlado por un mecanismo de transferencia de presión, y este mecanismo es probablemente la principal influencia en la cinemática del deslizamiento.摘要深位滑坡是非常复杂的系统。在许多情况下,需要进行多学科研究渗入了解可影响时空演化的关键特征。调查了意大利亚平宁山脉北部的Berceto深位滑坡,就是为了明确地下水的成因和地球化学演化过程,确定边坡系统水文边界,突出滑坡体内部的地下水水流通道、经过时间和运移形态。本研究基于一种多学科方法,该方法涉及到监测地下水位、获取水化学和稳定同位素和非稳定同位素(δ18O-δ2H, 3H, 87Sr/86Sr)分析结果、进行土壤滤淋试验、地球化学模拟以及主要成分分析。δ18O-δ2H 和 87Sr/86Sr分析结果显示,Berceto滑坡中的地下水补给源是当地的雨水,当地河流外部的补给可以排除。在滑坡体中,确定了两种地下水水类型(Ca-HCO3 和 Na-HCO3),地球化学模拟和主要成分分析结果确认,地下水的化学特征依赖于出现在滑坡内的水岩相互作用过程。3H含量表明,地下水为近代成因,似乎显示出浅层地下水和深层地下水的混合。3H含量和地下水位数据确认,浅层地下水主要受控于质量传输机制。3H分析结果和地下水位还表明,只有深层地下水受控于压力传输机理,这个机理可能是滑坡动力学的主要影响因素。ResumoEscorregamentos profundamente arraigados são sistemas complexos. Em muitos casos, estudos multidisciplinares são necessários para desvendar as principais feições hidrogeológicas que podem influenciar sua evolução no espaço e no tempo. O deslizamento profundamente arraigado Barceto, no norte dos Apeninos da Itália, tem sido investigado para definir a origem e evolução geoquímica da água subterrânea (AS), para identificar o limite do declive do sistema hidrológico, e destacar os caminhos de fluxo da AS, o tempo de trânsito e as modalidades de transferência dentro do corpo de escorregamento. Esta pesquisa está baseada e uma abordagem multidisciplinar que envolve monitoramento do nível da AS, obtenção de analise química da água e isótopos estáveis e instáveis (δ18O-δ2H, 3H, 87Sr/86Sr), realização de testes de lixiviação de solo, modelagem geoquímica (PHREEQC) e analise de componentes principais (ACP). Os resultados das análises de δ18O-δ2H e 87Sr/86Sr mostraram que a fonte de recarga da AS do escorregamento Berceto é a precipitação local e as contribuições externas de um fluxo local pode ser excluída. No corpo do escorregamento, foram identificados dois tipos hidroquímicos (Ca-HCO3 e Na-HCO3) e os resultado do PHREEQC e ACP confirmam que as características da AS depende do processo de interação água–rocha ocorrendo dentro do escorregamento. O conteúdo de 3H sugere uma origem recente da AS e parece destacar mistura entre as alíquotas de AS profunda e superficial. O conteúdo de 3H e níveis de AS confirmam que a AS superficial é controlada principalmente pelo mecanismo de transferência de massa. A análise do 3H com o nível de AS também indica que apenas a AS profunda é controlada por um mecanismo de transferência de pressão, este mecanismo é provavelmente a principal influência na cinemática do escorregamento.