12,723 research outputs found
Dinamiche di ricarica nella conoide del Trebbia
No full textANALIZZARE LE SERIE TEMPORALI DEI LIVELLI PIEZOMETRICI DELLE ACQUE SOTTERRANEE E DEI LIVELLI DEI CORSI D’ACQUA PERMETTE DI OTTENERE INDICAZIONI PRELIMINARI IN MERITO ALLE DINAMICHE DI RICARICA NATURALE DEI CORPI IDRICI SOTTERRANEI IN PARTICOLARI CONTESTI TERRITORIALI. LO STUDIO SULLA CONOIDE DEL TREBBIA NEL PIACENTINO
Hydrogeological characterization of peculiar Apenninic springs
No full textIn the northern Apennines of Italy, springs are quite widespread over the slopes. Due to the outcropping of low-permeability geologic units, they are generally characterized by low-yield capacities and high discharge variability during the hydrologic year. In addition, low-flow periods (discharge lower than 1 Ls-1) reflect rainfall and snowmelt distribution and generally occur in summer seasons. These features strongly condition the management for water-supply purposes, making it particularly complex. The "Mulino delle Vene" springs (420 m a.s.l., Reggio Emilia Province, Italy) are one of the largest in the Apennines for mean annual discharge and dynamic storage and are considered as the main water resource in the area. They flow out from several joints and fractures at the bottom of an arenite rock mass outcrop in the vicinity of the Tresinaro River. To date, these springs have not yet been exploited, as the knowledge about the hydrogeological characteristics of the aquifer and their hydrological behaviour is not fully achieved. This study aims to describe the recharge processes and to define the hydrogeological boundaries of the aquifer. It is based on river and spring discharge monitoring and groundwater balance assessment carried out during the period 2012–2013. Results confirm the effectiveness of the approach, as it allowed the total aliquot of discharge of the springs to be assessed. Moreover, by comparing the observed discharge volume with the one calculated with the groundwater balance, the aquifer has been identified with the arenite slab (mean altitude of 580 m a.s.l.), extended about 5.5 km2 and located 1 km west of the monitored springs
La subsidenza nella Pianura Padana come combinazione di processi naturali ed effetti antropici
No full textNel presente lavoro analizzeremo come la combinazione di fenomeni naturali come le varia-
zioni pluviometriche e la diversificazione dei processi antropici influenzino il fenomeno della
subsidenza nella Pianura Padana. Nell’intervento verranno illustrati i risultati ottenuti ana-
lizzando i dati acquisiti da una rete di stazioni GNSS permanenti e da una rete di pluviometri
e piezometri distribuiti nel settore orientale della Pianura Padana, con particolare attenzione
all’area metropolitana della città di Bologna
Temporal and spatial analysis of relative sea-level changes across the Emilia-Romagna coastal plain (northern Adriatic Sea)
No full textSea-level rise coupled with subsidence, namely relative sea level, currently represents the greatest threat to low-lying coastal areas worldwide, leading to a constant increase in flooding risks and shoreline erosion. The Emilia-Romagna coastal plain in northern Italy, facing the Adriatic Sea, is highly urbanized and critically important to the national economy. However, the entire area is prone to high flooding risks due to its low altitude and the limited resilience of the shoreline, which also results from anthropogenic modifications mainly started from the 1950s. In this study, a refined local geocentric sea-level time series for the period 1993–2020 has been reconstructed by processing data from tide gauges and satellite altimetry. Additionally, to assess the influence of vertical land movements on the relative sea level, InSAR datasets available from 2006 to 2020 have been incorporated into the analysis. After signal processing, time series representing relative sea-level changes across the entire coastal plain were produced on a spatial grid with a resolution of 500x500 meters. A relative sea level rise, ranging from 55% to 640% stronger than the geocentric one, is observed across the entire domain, with critical spots due to localized subsidence related to underground fluid exploitation, leading to severe flooding threats
Detecting natural and anthropic effects on displacements and water level changes: a combined observation from rain gauges, piezometers and CGNSS
No full textThe Po Plain (Northern Italy) has largely subsided due to natural processes and human activities. In particular, in order to reduce subsidence, in the Bologna metropolitan area a politic decision in 2010, imposed a significant reduction of civil water supply from groundwater withdrawal wells. The study area is characterized by an excellent monitoring activity which provides a good spatial and temporal distribution of data coming from continuous GNSS sites, piezometers and rain gauges.
In the present work we analyze both GNSS and piezometric data by means of the Principal Component Analysis (PCA). The results of the analysis are then compared with the rainfall time series measured by rain gauges. Thanks to the PCA analysis we can identify: i) a clear increase in the water level following the withdrawal decrease started in 2010 and ii) an anthropic induced surface displacement, which is smaller in magnitude than that induced by rainfall variations. Without the PCA analysis, such a small, but still significant, anthropic effect on vertical displacements would have remained hidden in the raw time series.
Our analysis reveals a decrease of about 4 mm/y of vertical velocity in some GNSS sites closest the withdrawal wells. We also found that on large time scales (> 1 month), the vertical displacement induced by rainfall strongly depends on the geological setting: in the mountains a water level increase causes subsidence (elastic response), whereas in the Po Plain it causes uplift (poro-elastic response). Thanks to the PCA analyses, the combined observations of different kind of instruments (GNSS, piezometers and rain gauges) and a basic knowledge of the geological context, we can correctly identify both the anthropic and natural signals on the data
Surface water-groundwater interaction and nitrate persistence in unconfined high-conductivity aquifers investigated via time series analysis
No full textGroundwater monitoring and protection are crucial issues within the environmental policies of the European Union. European directives require to (i) identify and characterize groundwater bodies, and (ii) reach specific quantitative/qualitative standards for each identified aquifer. The Italian laws incorporate these indications and provide technical criteria to characterize groundwater bodies. In this context, strategies aimed at preventing groundwater depletion play a relevant role in the conservation of water resources. In this study, we focus on the analysis of the underlying mechanisms of natural recharge for an unconfined high-conductivity aquifer. In particular, we refer to the area of the Apennines alluvial fan of the Emilia-Romagna Region. The portion of the cones close to the Apennines consists in high-permeable deposits that extend up to several hundred meters underground. A monolayer phreatic aquifer, connected directly to the surface, is located in this area. Widespread water withdrawals are present for agricultural and industrial purposes. For this reason, the analysis of nitrate concentration in groundwater represents a crucial issue. The use of nitrogen fertilizers and spreading of sewage and sludge in the soil are considered the main sources of nitric pollution. Based on time series analysis, we investigate the natural recharge dynamics by observing the influence of hydrometric variations on the piezometry, and the relationship between water level and nitrate concentration in the aquifer. We do this by means of autoregressive moving average models. The basic idea is to represent hydrological time series as single realizations of stochastic processes. In this context, we provide a basis to estimate groundwater vulnerability through an insight on surface water-groundwater interaction, and the persistence associated with nitrate concentration in an unconfined high-conductivity aquifer
The interaction between displacements and water level changes due to natural and anthropogenic effects in the Po Plain (Italy): the different point of view of GNSS and piezometers
No full textLike other sedimentary plains, the Po Plain in Northern Italy has largely subsided due to natural processes and human activities. Displacements of the Earth surface of hydrological origin are caused by groundwater changes, which in turn, are expected to be related to rainfall changes. In the Bologna metropolitan area (located in the Southeastern border of Po Plain), the 2010 politic decision of dismissing civil water supply from the groundwater withdrawal has provided us the opportunity to test a methodology for the retrieval of an anthropic effect in two different data sets: vertical displacements measured by continuous GNSS sites and piezometric water table fluctuations. The data sets have been analyzed by means of the Principal Component Analysis (PCA) and compared to rainfall time series from the Po Plain rain gauges. Several piezometers undergo a clear increase in the water level following the withdrawal decrease. Differently, the anthropic induced surface displacements are significantly smaller than the ones induced by rainfall. Accordingly, without a multivariate analysis such an effect on vertical displacements would have remained hidden in the raw time series. Only looking at the spatial distribution of the principal components we have highlighted that anthropic effects are local and present even in GNSS data, entailing for the 2010 case a decrease of about 4 mm/y of vertical velocity in some sites closest the withdrawal wells. Moreover, the multivariate analysis allowed us to assess that, on time scales larger than months, the rainfall-related hydrological response of vertical displacement depends on the geological setting. In the Apennines chain a water level increase causes subsidence, in agreement with the predictions of elastic models, whereas in the Po Plain it causes uplift, suggesting a dominant poro-elastic response, in agreement with the guess that the subsidence of the Po Plain is related to soil compaction. Our results suggest that in cases of the aquifers over-exploitation, a PCA analyses and the combined use of different observables such as GNSS, piezometers time series, rainfall data, geological setting allow getting a correct identification of the anthropic and natural signals
MABS validation through repeated execution and data mining analysis
No full textAgent Based Modelling is the most interesting and advanced approach for simulating a complex system: in a social context, the single parts and the whole are often very hard to describe in detail. Besides, there are agent based formalisms which allow to study the emergency of social behaviour with the creation and study of models, known as artificial societies. Thanks to the ever increasing computational power, it's been possible to use such models to create software, based on intelligent agents, which aggregate behaviour is complex and difficult to predict, and can be used in open and distributed systems. Data mining is born in the last decades in order to help users in finding useful knowledge from the otherwise overwhelming amount of data available nowadays from the web and the data collected every day by companies. Data Mining techniques can therefore be the keystone to reveal non-trivial knowledge expressed by the initial assumption used to build the micro-level of the model and the structure of the society of agents that emerged from the simulation
The use of stable water isotopes from rain gauges network to define the recharge areas of springs: Problems and possible solutions from case studies from the northern Apennines
No full textGli isotopi stabili dell’ossigeno e dell’idrogeno sono ampiamente utilizzati in bibliografia per la definizione degli areali di ricarica delle acque sotterranee in ambienti montani. Nella quasi totalità dei casi, vengono utilizzate relazioni pregresse sviluppate da altri autori che legano la variazione degli isotopi raccolti presso pluviometri campionatori con la quota, ricavando, con le sole analisi delle acque sotterranee, la quota media di infiltrazione delle acque sorgive campionate. Tale approccio, seppur di facile utilizzo, non tiene in considerazione i meccanismi di ricarica delle acque sotterranee, assumendo le acque campionate ai pluviometri come totalmente equiparabili alle acque sorgive. Dal punto di vista idrogeologico, tale assunzione non tiene in considerazione l’equazione del bilancio idrogeologico, trascurando gli effetti dell’evapotraspirazione e del deflusso superficiale. La presente nota riporta una comparazione preliminare tra isotopi stabili in acque meteoriche (1 pluviometro) e sotterranee (2 sorgenti) nel medio-alto Appennino emiliano. I risultati evidenziano come, nel caso in esame, le relazioni comunemente applicate in bibliografia forniscano valori di quote di alimentazione fuorvianti, in entrambi i casi superiori alle rispettive quote massime dei bacini idrogeologici delle sorgenti. Le stime dell’evapotraspirazione potenziale, e la successiva procedura dei weighting del dato isotopico meteorico, sottolineano come la causa principale delle anomalie nella stima della quota di alimentazione sia da ricercare in questo parametro del bilancio, che non consente alle acque meteoriche estive di pervenire alle falde sotterranee
Different corrosive effects on hydroxyapatite nanocrystals and amine fluoride-based mouthwashes on dental titanium brackets: a comparative in vitro study
No full textTitanium plates treated in vitro with a mouthwash containing amine fluoride (100 ppm F-) and another containing zinc-substituted carbonate-hydroxyapatite have been analyzed by scanning electron microscopy and atomic force microscopy to evaluate the modification of the surface roughness induced by treatment with these two different mouthwashes. The treatment with F--based mouthwash produces a roughness characterized by higher peaks and deeper valleys in the streaks on the titanium bracket surface compared with those observed in the reference polished titanium plates. This effect causes a mechanical weakness in the metallic dental implant causing bacterial growth and therefore promotes infection and prosthesis contamination. However, the in vitro treatment with a mouthwash containing zinc-substituted carbonate-hydroxyapatite reduced the surface roughness by filling the streaks with an apatitic phase. This treatment counteracts the surface oxidative process that can affect the mechanical behavior of the titanium dental implant, which inhibits the bacterial growth contaminating prostheses
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