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The circulation of karst water in evaporate terrains (e.g. salt beds, gypsum or anhydrite) may develop long circuits and important morphologies both on the surface and underground. The features of these karst circuits are strongly conditioned by the high solubility and the low mechanical strength of the rock, resulting in a high propensity to develop collapses and subsidence morphologies on the surface (e.g. sinkholes). Nevertheless, the attention of the scientific world was often more focused on karst systems in carbonate rocks that rise interest for the utility of water as drinking resource. Karst aquifers in carbonate rocks (e.g. limestones and dolomite), indeed, often represent an important source of high-quality water, while in evaporite terrains the high salinity of the water usually prevents the use of the aquifers for drinking purpose. The investigation of karst systems in gypsum and anhydrite terrains, however, covers an important role in the minimisation and prevention of risks connected with the interference with civil infrastructures. In particular, karst phenomenon represents one of the main risk factors for the stability and safety of gypsum quarries, especially if underground. The possible filling with clay or pressurized water of the karst cavities exponentially increases the dangerousness of the phenomenon, due to swelling problems and violent water inrushes. If not carefully evaluated, the interference between karst systems and quarry activity may evolve in risk scenarios for the stability of underground tunnels and for the surrounding environment, inducing collapses of karst caves and underground quarry structures, slop instabilities, subsidence phenomena on the surface and modification of the hydrogeological setting of the area. In this study, the features and the development of karst systems in gypsum are described and monitored in correspondence of a series active quarry sites. The karst morphologies are investigated with non-destructive geophysical techniques. Test sites were chosen in the Monferrato area that hosts some of the main gypsum bodies of Italy. The results of the geophysical investigation are integrated with the known geological features of the sites, in order to obtain a more complete and reliable description and interpretation of the phenomenon.

SGI 2021

Karst morphologies and related risks in gypsum of Monferrato area (NW Italy)

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L'Istituto Nazionale di Oceanografia e Geofisica Sperimentale - OGS e il Dipartimento di Matematica e Geoscienze dell'Università di Trieste sono orgogliosi di ospitare il 90° Congresso della Società Geologica Italiana a Trieste dal 14 al 16 settembre 2021. La modalità del congresso è interamente online.

Con il motto "Geologia senza frontiere" questo evento mira a promuovere le Scienze della Terra come disciplina scientifica proiettata nel futuro, oltre i confini geografici, politici e disciplinari, per comprendere meglio l'interno del Pianeta Terra e la struttura del sottosuolo, difendere la società da pericolosi eventi geologici, comprendere meglio la variabilità climatica, pianificare l'utilizzo delle georisorse in modo etico e nel rispetto dell'ambiente.


**Please note, times listed in the SCHEDULE tab (calendar icon) reflect YOUR LOCAL TIME ZONE. The main timezone for this conference will be Central European Summer Time.**

The National Institute of Oceanography and Experimental Geophysics - OGS and the Department of Mathematics and Geosciences of the University of Trieste are proud to host the 90th Congress of the Italian Geological Society in Trieste on 14-16 September 2021.  The Congress will be held entirely online.

With the motto "Geology Without Borders" this event aims to promote Earth Sciences as a scientific discipline projected into the future, beyond geographical, political and disciplinary boundaries, to better understand the interior of Planet Earth and the structure of the subsurface, defend society from dangerous geological events, better understand climatic variability, plan the use of geo-resources in an ethical way and respecting the environment.


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Earth Sciences should be understood not only as necessary for a better understanding of the interior of the planet Earth, but also as a defense of society from dangerous geological events, for the understanding of climatic variations, for the planning and use of georesources in a ethical and respecting and protecting the environment.

technical paper

The use of renewables is of paramount importance for sustainable development and economic growth. In this context, shallow ground-sourced heat exchangers (GSHEs) coupled with geothermal heat pumps represent a valuable opportunity for heating and cooling systems both in urban and rural areas. The regions of the Central Italy affected by the 2016 seismic sequence (Mmax 6.5), while involved in the post-earthquake reconstruction, could greatly benefit from the installation of GSHEs, which are environmental-friendly and with two peculiarities among the renewables: (i) continuous source of thermal energy and (ii) landscape protection (GSHEs are not visible). Here the focus is set on the evaluation of the shallow geothermal potential for the southern sectors of the Marche Region, with the aim of producing maps favouring the knowledge of the heat that could be extracted through GSHEs from different rocks of the subsoil. As a first pilot area we selected the upper-middle portion of the Potenza river fluvial plain to quantitatively estimate the values of key parameters such as the thermal conductivity, the volumetric heat capacity of the subsoil and the specific heat extraction. We followed the methods described in Taussi et al. (2021), thus averaging the geothermal parameters values over the first 100 meters, i.e. the most common depth of GSHEs. In order to assign the representative values for the shallow heat exchange parameters, the local stratigraphy was reconstructed on the basis of the surveys and data (mainly geognostic drillings) made available by the Civil Protection, thanks to the completion of the third level of the seismic microzonation studies. This freely accessible database might represent a valuable tool and source of information for such shallow geothermal studies in many different areas, and thus we recommend its use, given the relatively easy availability. In addition, the possibility (and the reliability) to use geophysical surveys (such as MASW or HVSR analyses) data, typically available in such databases, will be tested in order to independently estimate and compare the values of the most relevant shallow geothermal parameters. Preliminary results indicate that higher values for thermal conductivity (> 1.9 W∙m-1∙K-1) and volumetric heat capacity (> 2.35 MJ∙m-3∙K-1) characterize the uppermost sector of the fluvial plain of the study area, especially those areas around San Severino Marche and the ridges corresponding to Treia and Pollenza, where the, respectively, carbonate and siliciclastic bedrocks occur at relatively shallow depths. The development of GSHEs for heating and cooling systems should be really regarded as an opportunity for the reconstruction of these areas hit by the 2016 earthquake.

Defining the shallow geothermal potential by using the seismic microzonation data: a case study from the Southern Marche Region to encourage a sustainable post 2016-earthquake reconstruction

In Ecuador, the Paute river basin is one of the most monitored due to its importance for the generation of hydroelectric energy (Amay & López, 2015). However, in recent years there have been problems related to dry seasons that limit the distribution of electrical energy for industrial and domestic purposes (Galárraga, 2000). The ETAPA company indicates a decrease in water quality in urban areas, since measurements were made in the upstream sections and in sections of rivers that cross the city of Cuenca (occupying 41.22% of the province) obtaining data that showed that the quality indices fall from an excellent-good classification for the high sections, to a good-average classification in the low sections (Amay & López, 2015). For this, it is essential to use hydrological simulation models in order to know the water dynamics that develops within a basin both in current and future conditions, one of them being the hydrological model known as SWAT, which was developed by the United States Department of Agriculture in conjunction with the University of Texas, whose objective is to quantify and predict the environmental impact that land use practices generate on the production of water (and its quality), sediments, nutrients and substances chemicals within a basin influenced by various factors such as the type and use of land and meteorological conditions (Ríos & Faustino, 2017). The aim of this study is to evaluate the efficiency of the SWAT model with respect to simulations of nitrates, organic phosphorus, dissolved oxygen, sediments and evapotranspiration using as reference data observed in continuous monitoring stations. The results showed that the correlation between the simulated and the observed data is practically null if a linear relationship were established between them (Pearson's correlation coefficient). On the other hand, the simulations overestimated the evapotranspiration, dissolved oxygen and sediment values; and underestimated the values ​​of nitrates and organic phosphorus, based on PBIAS%. The RSR statistical criterion indicates that the modeling performance is unsatisfactory for nitrates, evapotranspiration and dissolved oxygen; and it is very good for organic phosphorus and the sediments of the “Llaviuco” station, which was verified with the application of the NSE statistical criteria. It is worth mentioning that the modeling in SWAT for this case study in general can be classified as poor because an initial calibration or correction of the model was not performed.

Evaluation of the SWAT model with respect to different variables within the Tomebamba River sub-basin belonging to the Paute River Basin-Ecuador

The realization of tunnels, boreholes or quarry drifts in evaporite terrains often brings to face issues related to the geological and physical peculiarities of these rocks. In particular, typical problems are caused by the swelling behaviour of anhydrite, the high solubility in water and the high heterogeneity of gypsum facies. All these problems are particularly evident in the framework of quarry exploitation: the stability of rock pillars in underground quarries requires dedicated investigations. This study proposes an analysis of the main parameters that may affect the stability of underground gypsum pillars, considering in particular the effect of material heterogeneity and relative humidity. With this aim, the study proposes an investigation of a strongly heterogeneous facies of gypsum from the Messinian Salinity Crisis (i.e. branching selenite facies from Monferrato area, NW Italy). The textural and microstructural heterogeneity of the material is described with different techniques (MIP and SEM analyses). The study then includes a series of ad hoc designed mechanical tests to quantify strength and creep in function of the relative humidity. Results show the clear influence of material heterogeneity on the mechanical response. To this intrinsic mechanical variability, the influence of an external parameter as the humidity is observed to generate an additional reduction of material strength and to increase the creep strain rate in the long term tests. The effect of all these elements in the framework of a real underground quarry site is eventually discussed.

Effect of material heterogeneity and environmental humidity on the stability of gypsum in underground quarries

Monitoring and analysis of groundwater levels in space and in time is one of the tools to evaluate the quantitative status of groundwater resources and identify the groundwater response to climate variability, possible alterations and critical cases (IAH, 2016). In this study daily groundwater levels (GWL) in 36 piezometers of the shallow unconfined aquifer, and rainfall (R) data of 26 rain gauges located in  the Piedmont plain (western Po Plain, NW Italy) were collected in 2002-2017 interval and analyzed. Monthly and yearly aggregated data were then elaborated. Four methods for the analysis of groundwater resources status were applied to GWL: trends identification with the application of the non-parametric Mann-Kendall test, change-points research with the application of Pettitt test, percentiles method proposed by ISPRA (ISPRA, 2017) and non-standardized anomalies analysis. The same analysis were applied to R time series. For GWL and R time series, correlations with monthly lags and coefficient of variation of the maximum annual fluctuations, were also evaluated. The application of different methods to the GWL series permitted to clarify the GWL evolution in time and the spatialization of results allowed us to identify four areas with a similar hydrodynamic behaviour and resource status: south-eastern sector (Alessandria plain), north-northeast sector (Vercelli-Novara plain - rice fields), western sector (Turin plain) and south-west sector (Cuneo plain). Furthermore, the most critical areas were identified and some potential factors (anthropic, geological and hydrogeological) conditioning the hydrodynamic behaviour of the water table levels were highlighted. All the methods identified a critical situation in the Alessandria plain. In addition, the comparison between R and GWL results provided information on the timing and pattern of aquifer recharge, the hydrodynamic behaviour of GWL and their link with R variability. At last, this multi-criteria approach allowed to highlight advantages and limits of the applied methods. Finally, the application of different methodologies made it possible to evaluate not only the state of the resource by highlighting possible trends and critical situations, but also the real impact of rainfall variations on GWL variations and to assess how and with what delay GWLs respond to rainfall. Future insights will analyse the effects of other natural factors (air temperature, evapotranspiration, snowmelt) and anthropogenic variables (extent of withdrawals), with an in-depth analysis of the local hydrogeological and geological characteristics of aquifers.

Application of different statistical methods for analysis of groundwater levels in time:  spatio-temporal analysis in Piedmont plain (NW Italy) and comparisons with rainfall time series

This study proposes a survey methodology for identifying areas for combined Sustainable Drainage Systems (SUDS) and Aquifer Storage and Recovery (ASR) (Dearden et al. 2013, Sharp Jr., 1997); these techniques exploit the hydrogeological and geomorphological characteristics of an area, to increase the natural infiltration capacity of water into the ground. The target area is the city of Rome and the aim of such techniques is to solve the problems related to rainwater which, in case of extreme events, struggles to infiltrate the ground, overloads the undersized hydraulic systems and floods the urban space. The proposed method involves GIS geospatial analysis of various data: the permeability of outcropping lithology, the piezometric level of the aquifer, hydrogeological units, geomorphology and land use. To identify the suitable areas, areas characterised by high permeability and a piezometric level that would confer a volumetric capacity to possibly store even large quantities of water, without triggering possible problems associated with fluctuations in the water table, were identified. The data were divided into classes and indexed in order to compare and overlap them. Finally, hydrogeological units were also taken into account (by analysing their depth trend) in order to identify areas with similar characteristics of permeability with respect to depth. The latter will also be compared with the previous data to identify the areas suitable for SUDS and ASR. The final product of the suitable areas from a hydrogeological point of view will be compared with the land use map in order to exclude those areas that, for administrative and other legislative reasons, cannot be destined to this kind of activities.

Identifying areas suitable for Sustainable Drainage Systems and Aquifer Storage and Recovery to mitigate stormwater flooding phenomena in Rome (Italy)

In Naturally Occurring Asbestos (NOA) rich areas, weathering and erosion of asbestos-bearing rocks (e.g. meta ophiolites) are likely to cause water asbestos pollution: this may occur as a consequence of superficial and groundwater flow through natural rock formations containing NOA, depending on the characteristics of either the rocks and hence the water. Concerning groundwater management in NOA settings, asbestos pollution has to be considered with regard to water quality assessment: it represents an environmental problem and could even constitute a risk for human health. In fact, waterborne asbestos can come into contact with human beings as airborne fibres after water vaporization, or by ingestion, especially if they are present in drinking water. While a lot is known about diseases caused by airborne asbestos respiration (e.g. IARC, 2012), not enough has been yet understood about potential noxiousness of its ingestion. Consequently, a Maximum Contaminant Level for asbestos in potentially usable water has not been defined yet (WHO, 2020). To investigate possible groundwater pollution by asbestos due to natural environmental causes, a study area was selected in Piedmont, nearby NW Alps which are rich in NOA (and naturally occurring asbestiform minerals non-asbestos classified) (Belluso et al., 2019). In this area, two sampling and analysis campaigns regarding surface waters and groundwater were settled to investigate if, how and which type of mineral fibres could occur in water, trying to correlate them to the geolithological and hydrogeological characteristics of the area. The results of the two campaigns will be presented aiming to investigate asbestos and asbestiform fibres occurrence in water in relation to hydrochemical parameters, which are expression of the local hydrology and geolithology, and to evaluate seasonal variability. In addition, asbestos (and asbestiform) fibres transportation due to water flowing in NOA settings will be tested with a physical model, since a recent study highlighted possible asbestos mobility through soil (Mohanty et al., 2021): guidelines to create a flow model which describes mineral fibres mobility in porous aquifers will be presented following laboratory tests based on contaminated water circulation through packed columns.

Groundwater asbestos contamination in Naturally Occurring Asbestos (NOA) rich areas: a study on fibres characteristics, concentration and their possible mobility in aquifers

It’s now recognized that a global climate change is taking place, leading to an increase in temperatures and a variation in precipitation regime, also affecting groundwater (GW) (Taylor et al., 2013).  In this study we want to evaluate how climate change affects GW temperature in the Piedmont Po plain (NW Italy). The Piedmont Po plain covers the 27% of the whole region and it’s the most important GW reservoir of the Piedmont region (De Luca et al., 2020). It consists, from top to bottom, by Alluvial deposit complex (lower Pleistocene-Holocene), that hosts a shallow unconfined aquifer, the “Villafranchiano” transitional complex (late Pliocene-early Pleistocene), that hosts a multilayered aquifer, and a Marine complex (Pliocene) hosting a confined aquifer (De Luca et al., 2020). For this research, 41 wells in the shallow aquifer and 20 weather stations were selected throughout the Piedmont Po plain area, and GW and air temperature parameters were analysed for the period 2010-2019. The GW temperature data were firstly studied with basic statistical analysis (mean, maxima, minima) and then with the Mann-Kendall and Theil-Sen methods to evaluate the trend of the monthly mean GW temperatures. GW temperatures show a general increase in all the plain, up to a maximum of 2.18 °C/10 years. The same analyses were carried out for the air temperature data and it was observed that the increases vary between 1.52 and 2.11 °C/10 years. Then to compare water and air temperature, the Voronoi polygons method was used on QGis by centring the polygons on the weather stations. From this comparison, it was possible to highlight that in most cases (37 on 41, thus 90% of the analysed couples of temperature data) there is a greater increase in the monthly mean air temperatures than in the monthly mean GW temperatures. The same behaviour was observed for the monthly minima and maxima GW and air temperature. These results testify a greater resilience of GW temperature to climate variability. Future insights will be a detailed analysis of the factors influencing the more or less evident increase in GW temperatures in relation to air temperatures (e.g. depth of the water table, position of the monitoring well, position of the probe inside the well...).

The impact of climate change on groundwater temperature of the Piedmont Po plain (NW Italy): preliminary results

Hydrogeological mapping represents an essential tool for groundwater resources management and to study regional-scale variations induced by anthropic pressure, climate change, and catastrophic natural events. The mountainous aquifers, in particular, represent the natural water towers of our planet. The Water Framework Directive 2000/60/EC establishes the action of water policy for the European Community. According to that, many water protection and management plans have been developed by the local authorities aiming at achieving the quali-quantitative targets for the protection of water resources and water bodies, ensuring a long-term sustainable water supply. The authority’s decisions are supported by hydrogeologists, with maps focusing on the main hydrogeological complexes of the national and local territories. For these purposes, a new regional-scale hydrogeological map has been realized regarding the southernmost mountainous part of the Marche Region, considering both the fractured carbonate reliefs of Sibillini Mts. and the “Laga” geological formation. This map extends from the upper portion of the Chienti river basin to the Tronto river basin and integrates both the discharge measurements conducted during the years and the information from different kind of maps, i.e. the official geological maps of Marche Region and other published maps (Pierantoni et al., 2013; Viaroli et al., 2021). The major tectonic lineaments have been interpreted from a hydrogeological point of view and reported on the map. Based on detailed geo-structural fieldwork performed in the area and on the available literature, the geological formations have been reclassified into homogeneous hydrogeological complexes. Operating in a GIS environment, they have been merged to obtain hydrogeological complexes. The boundaries of these complexes lying below the Quaternary deposits have been inferred. The main punctual and linear springs of the area have been included in the map. Spring discharge has been measured using both hydrometric current meters and artificial tracers and they have been added to the discharge data provided by drinking water companies of the area. The new map can be used as a visual decision support tool to evaluate water resources in these highly productive but relatively unexplored areas and will provide an updated database on water resources availability to the Marche Region and other public authorities.

Hydrogeological map of the Southern mountainous portion of Marche Region (Central Italy)

The hydrodynamic behavior of karst aquifers is usually complex due to the high degree of heterogeneity and anisotropy of their geologic and hydrogeologic properties. Among karstified rocks, metamorphic carbonate rocks (e.g marble and meta-dolostone) are characterized by very low porosity and permeability, but their hydraulic properties can be altered by geologic processes, and significant aquifers can develop into these rocks eventually. However, the functioning of metamorphic karst aquifers is still poorly known. This contribution presents the hydrological monitoring of three of the main karst springs of the Apuan Alps (Italy). This mountain chain is characterized by extensive metamorphosed carbonate outcrops in which karst aquifers have developed. Pollaccia, Renara and Equi springs were equipped with multi parametric sensors for water level and discharge (L, Q), temperature (T), and electrical conductivity (EC). Their hydrographs and chemographs were compared with precipitation time series collected by the meteorological stations to investigate the response of the karst systems to infiltration and to infer their structure. The mean discharge for Pollaccia, Renara and Equi springs were respectively about 900, 200 and 800 l/s, their EC varied between 130 and 300 µS/cm, whereas T ranged between 7.8 and 10.6 °C. Water discharge, T, and EC response to infiltration was quick and impulsive with lag times of few hours. EC and T trends were complex for all the three springs, but dilution was the prevalent hydrodynamic response to precipitation observed during the monitoring. Piston-flow phenomena were scarce and limited to particular conditions. No delay between discharge increments and EC and T responses occurred. These observations suggest that the springs are fed by dominant conduit systems in which water flows only in few, enlarged conduits, with limited fracture storage. Piston-flow phenomena could be related to the presence of secondary flow networks that are connected with the main flow pathways only in specific conditions and/or to the flushing of limited volumes of water stored in the aquifers. Monitoring results suggest that the functioning of meta-carbonate aquifers in the Apuan Alps is controlled by several factors such as the low degree of fracturing of marbles, the local structural arrangement, and the primary porosity of the karstified rocks. As a consequence, storage is limited and flow velocity is high, preventing sustained water-rock interactions.

Monitoring karst aquifers hydrodynamics in metamorphic carbonates: the example of the Apuan Alps, Italy

The north-western sector of the Friuli Venezia Giulia Region, on the border between Italy and Austria, is characterized by the presence of an extensive mountain massif where outcrop the intensely karstified Devonian limestones. The high average rainfall, together with the high permeability of carbonates, has favored the development of an extensive aquifer, the main source of which is represented by the Fontanon di Timau. Due to its high flow rate, between 250 and 5000 l/s, the spring is exploited both for the supply of drinking water and hydroelectric energy. Given the importance of the source, a research project has started, partially funded by the Geological Service of the Friuli Venezia Giulia Region, aiming at the hydrogeological characterization of the survey area in order to identify the its recharge area and evaluate its vulnerability. The present paper proposes a hydrogeochemical characterization of precipitation, surface waters and springs in the area located between Mt. Coglians and the Alta Valle del But, and between Eiskar glacier, the valley of the Valentina and the Anger valley for the Italian and Austrian sectors, respectively. The study was carried out over a period of about 5 years, during which a hydrogeological survey was carried out in order to identify all the sources present in the area and to design a geochemical monitoring network of the waters. Thanks to special rain gauges, monthly precipitations were collected for the isotopic composition analysis in order to determine the isotopic gradient of the area (Plocken, Mt. Croce Carnico, and Rivo). Surface and spring water samples were collected for the study of stable (O and H), unstable (3H) isotopes, radionuclides (Rn), major and trace elements. The trends related to the temperature and electrical conductivity of the water in correspondence of different sampling points were also defined. At the same time, tracing tests were also performed using uranine and tinopal, which made it possible to verify the hydrogeological connection between the western sector of the karst area and the Fontanon di Timau and to define the hydrodynamics of the underground system. Isotopes and trace element results highlighted that Fontanon di Timau spring is significantly fed by the massif of Mt. Coglians-Creta di Collinetta as well as by the waters that infiltrate the area of Pal Piccolo-Creta di Timau and partially also from the waters that infiltrate beyond the watershed in Austrian territory. All the other springs identified in the area, on the other hand, have much lower flow rates and drain waters from neighboring basins limited to the Italian side only.

Karst morphologies and related risks in gypsum of Monferrato area (NW Italy)

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Defining the shallow geothermal potential by using the seismic microzonation data: a case study from the Southern Marche Region to encourage a sustainable post 2016-earthquake reconstruction

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Geochemical characterization of the Timau Karst aquifer

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Karst morphologies and related risks in gypsum of Monferrato area (NW Italy)

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Next from SGI 2021

Defining the shallow geothermal potential by using the seismic microzonation data: a case study from the Southern Marche Region to encourage a sustainable post 2016-earthquake reconstruction

Similar lecture

Geochemical characterization of the Timau Karst aquifer

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES

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