1,721,015 research outputs found
Idrogeologia del massiccio carbonatico della montagna della Majella (Appennino centrale
No full text27ff., 9 tabb., 2 tav.f.t. Pubbl. CNR/GNDCI n°263
Stationary and non-stationary geostatistics to model 3-D hydraulic conductivity distribution: a case study in the southern Po river plain
No full textGroundwater numerical modeling has become one of the most important up-to-date water resource management tools because it allows to reproduce the aquifer behavior, that is vital in sustainable water resource exploitation, contamination fate assessment, and remediation scheme design and efficiency evaluation. During numerical model implementation, besides the hydrogeological boundary conditions, the hydraulic conductivity (K) of the considered aquifer is a key parameter to be defined. In general, this parameter is assigned to each hydrogeological complex, relying on values obtained by point permeability tests (e.g. pumping tests, slug tests, etc.). Although the obtained experimental K values could be representative of a portion of the whole aquifer volume, its intrinsic heterogeneities cannot be detected, especially when the considered aquifer is very complex (Bianchi & Pedretti, 2017).
For this reason, the main objective of the research is to draw a physically based 3-D hydraulic conductivity model by both stationary (i.e. Ordinary Kriging, OK) and non-stationary (Intrinsic Random Function theory, IRF-k) geostatistical methods, applying these techniques to 182 Cone Penetration Test (CPT) profiles of the tip (qc) and shaft (fs) resistances, collected by the Emilia Romagna Regional Geological Survey. The obtained 3-D qc and fs models were combined by equations present in literature (Robertson, 1990; Lunne et al., 1997) to obtain the lithology index (Ic) and the K models.
The selected study area is in the southern part of the Po plain and is characterized by mainly alluvial deposits made up of undifferentiated fine silty-sandy deposits, with coarser (i.e. sandy gravelly alluvial fans and sandy paleo-channels) and finer (i.e. silty clayey lacustrine lenses) geological inclusions.
As a result, the OK and IRF-k method allowed to estimate the K values in a 3-D model, starting from CPT data. The obtained models reproduce as closely as possible the actual geological and hydrogeological features, not neglecting the multi-scale heterogeneity. The proposed methodological approach provides a detailed physically based 3-D hydraulic conductivity model. The obtained 3-D K model can represent a useful starting point for hydrogeological numerical modeling and/or a constraint for model calibration, especially when the intrinsic deposit heterogeneity could affect substantially the groundwater flow and contaminant transport in the aquifer
Groundwater management in Central Italy (Latium and Abruzzo): current uses and future risks.
No full textThe role of snow melting and rainfall on the discharge and physico-chemical characteristics of springs: a statistical analysis in Central Apennines
No full textIn this study, the statistical relations between meteorological recharge and hydrodynamic and hydrochemical behavior of the Verde spring, the main discharge of the Majella Carbonate aquifer system (central Apennine) exploited for drinking and hydroelectric purposes, were synthesized.
The results allowed to identify several flow paths, characterized by different sizes, hydraulic conductivities, and distances from the spring, that get activated depending on the type (rain or snowmelt) and the amount of the inflow.
In order to get a deeper insight on the Majella system groundwater flow, multiparameter daily time-series were considered, all related to the same time period (1803 days; about 5 years between 1997 and 2002) and collected in different monitoring point all over the Majella aquifer. In detail, they were analyzed: the snow cover thickness, the rainfall data, the Verde spring discharge, the electrical conductivity and temperature of the Verde spring.
The raw and residual multiparameter time-series were then analyzed by the Autocorrelation Function (ACF) and Cross-Correlation Function (CCF), to investigate how the spring parameters react to the different inflows.
The results obtained by the ACF and the raw and residual CCFs, together with the knowledge of the hydrogeological features of the Majella aquifer, allowed to implement a refined conceptual model.
The Autocorrelation analysis showed that the variability of the spring discharge and Electrical conductivity time-series can be accounted by the combined effect of both rainfall (i.e. random component) and snowmelt (i.e. systematic component) recharge.
The results obtained clearly demonstrated that the snowmelt contribution is predominant with respect to the rainfall one. The travel times in the unsaturated and saturated zones of the water moving toward the Verde spring and the aquifer recharge modes depend on the different inflows (i.e. snowmelt and rainfall), their distribution in the recharge areas, their intensity and distribution in time. In detail, the multiparameter time-series analyses allowed to identify several recharge modes related to different flow paths, that are characterized by different sizes, hydraulic conductivities and distances from the spring, in both the unsaturated and saturated zones.
The level of detail obtained by the multiparameter time-series analyses is high, although below the one provided by tracer tests. In fact, this methodological approach allowed to account for small changes in the spring parameters, such as the electrical conductivity (about ± 15 S/cm) and temperature (about ± 0.1° C), that are considered meaningless.
The study demonstrated that the multiparameter hydrodynamic and hydrochemical time-series analyses, related to heterogenous fractured and/or partially karst aquifer systems, can provide more detailed information about the groundwater flow and the recharge modes, without using tracer tests
Reactive transport modeling for the evaluation of field scale substrate competition in a complex contaminated site
No full textWithin a plume, the redox processes are the main driver of pollutants’ behavior and fate. In fact, when fuel-derived organic compounds, such as BTEX and MTBE, are released in groundwater, they degrade by direct mineralization or fermentation. The oxidation of the primary substrate and/or the fermentation by-products, such as H2 and Acetate, (electron donors) obviously triggers the reduction of redox-sensitive compounds (electron acceptors) naturally present and/or anthropogenically released in the aquifer, well known as Terminal Electron Accepting Process (TEAP). The TEAP is catalyzed by different microbial species, each one utilizing the available substrate and a corresponding electron acceptor. Thus, if in the same polluted site, in addition to endogenous electron acceptors (i.e. Nitrate, Mn(III/IV) hydr-oxides, Fe(III) hydr-oxides, Sulfate, etc.), chlorinated ethenes (i.e. PCE, TCE, DCEs, VC) are present, reductive dichlorination process could likely be inhibited, because of the competition among the corresponding microbial species.
In order to deepen these issues, the modeling of reactive transport has been applied, simulating the degradation processes and interaction among several compounds along the main flow path (1-D model) in a coastal aquifer, where 10-15 meters thick sandy and silty sandy deposits aquifer overlay an clayey aquiclude. Here, several foundry wastes burials (high content of Mn and As-rich Fe hydr-oxides), an oil spill from a fuel station tanks and a residual chlorinated solvents residual phase were revealed.
For kinetically controlled processes (i.e. fuel-derived organic compounds degradation and reductive dechlorination), different equations have been used and compared: the first-order equation, the Michaelis-Menten equation, and the Monod equation. The simulation has been performed by means of the software Phreeqc and the results validated using chemical analyses made on groundwater samples collected in a 43 well monitoring network.
The first results show a persistence of reductive dechlorination by-products (i.e. DCEs and VC) in groundwater, near the largest foundry wastes burial. In fact, the correspondence between the high concentration of DCEs and VC and the high concentration of Mn, Fe and As in groundwater suggests a strong competition for the substrate
MUD VOLCANOES IN CENTRAL ITALY: SUBSOIL CHARACTERIZATION THROUGH A MULTIDISCIPLINARY APPROACH
No full textMud volcanoes are common geological phenomenons observed worldwide as in Italy. They are well described in the scientific literature for their morphological, tectonic and hydrogeological features. They represent not only a relevant geological and geomorphological interest but also not negligible elements of hazard and risk associated with the presence of soft and pliable sediments and with the possible unexpected emission of gas and mud. Therefore, the understanding of their structure and hydrogeological circuits in the subsurface is an important key to define hazard and risk conditions in the adjacent areas.
This paper deals with a multidisciplinary study including geophysical and hydrochemical surveys undertaken at the Pineto (central Italy) mud volcano site to achieve an interpretative conceptual model explaining the shallow upward migration of deep mud fluids. Shallow electrical and seismic imaging of the mud volcano was obtained using two dimensional and three dimensional (2D–3D) electrical resistivity tomography and 2D reflection seismic surveys. The hydrochemical properties of the rising fluids were assessed by means of seasonal measurements of the chemical–physical parameters, the concentrations of major ions, and some natural isotopes. This mud volcano or mud lump appears as a dome of about 15 × 10 m in size. The height of the crater is 2 m approximately, while the diameter of the crater is 2.5 m. Emission of fluids and solids (cold brine, mud, gas) occurs from this crater. Upper Pliocene–lower Pleistocene foredeep pelitic deposits (over-compacted clays with silty–sandy levels) overlain by clayey–silty deposits crop out in the area. The survey results seem to reveal that the uprising of deep fluids does not occur exactly below the mud volcano at present. Instead, a high conductivity body is present within a fractured zone in the pelitic deposits at 60 m approximately to the ENE. The probable occurrence of a high permeability layer approximately between 20 and 30 m below ground level, confined by clay deposits, gives rise to an overpressured mud fluids reservoir. Mud fluids appear to be flowing toward the surface from the reservoir up to the mud volcano crater. The interpretative conceptual model proposed by the authors is a first attempt to explain the shallow upward migration of deep mud fluids in this central Italy mud volcano. The results can be used to identify the uprising of fluids with similar chemical–physical properties even in areas where the superficial and morphological evidence of the volcanic bodies have been obliterated or covered
1-D reactive transport modeling to evaluate the interaction among different compounds in a complex contaminated site driven by redox processes
No full textThe redox processes are the main drivers that condition the behaviour of different compounds within a plume in a contaminated site. The fuel-derived organic compounds (BTEX and MTBE), that can be released in the aquifer through an oil spill, trigger in groundwater heavy redox condition. This is due to the direct mineralization of organic matter (Palmucci et al., 2016) or to the mineralization of fermentation by-product (e.g. H2, Acetate, Phenol, etc.), that represent the substrate for microbial growth (Watson et al., 2003; Chambon et al., 2013). When a contamination by chlorinated ethenes (i.e. PCE, TCE, DCEs, VC) also occur, the reductive dechlorination process, which leads to their degradation, can be inhibited by others redox-sensitive compounds (i.e. NO3-, Mn(III,IV) hydr-oxides, Fe(III) hydr-oxides, SO42-, etc.) naturally and/or anthropically present in the aquifer, because of the competition among the corresponding microbial species (McCarty, 1997; Chambon et al., 2013). The modeling of reactive transport, considering and comparing different kinetic degradation equations (e.g. first-order equation, Monod equation, etc.), can be considered an up-to-date method to understand in detail the processes occurring within the plume, in order to evaluate the best remediation technique.
As study area, a coastal aquifer has been selected, where 10-15 meters thick sandy and silty sandy deposits aquifer overlays an clayey aquiclude (Desiderio & Rusi, 2003; Di Curzio & Rusi, 2016). Here, several foundry wastes burials, an oil spill from a fuel station tanks and a residual chlorinated solvents residual phase were detected.
The reactive transport has been simulated along the main flowpath (1-D model) using Phreeqc (Appelo & Postma, 2005) and the dataset used for the model validation consists of chemical analyses made on groundwater samples collected in a 43 wells monitoring network.
The first results show a persistence of reductive dechlorination by-products (i.e. DCEs and VC) in groundwater near one of the largest discovered foundry wastes burial containing Mn and As-rich Fe hydr-oxides. Thus, the higher is the metals' content in the solid matrix, the slower is the progress of reductive dechlorination, suggesting a strong competition for the substrate among the different microbial species
Hydrogeology, aquifer vulnerability and potential hazard of the Sulmona plane ( Central Apennine, Italy ).
No full textAbstract
The results of hydrogeological studies carried out on some hydrostructures in the central Apennines are reported. The hydrostructures studied are representative of the hydrogeological characteristics of the Apennine limestone ridges.
The vulnerability of the aquifers and springs present in the hydrostructures was analysed and the results show that this is very high
Multidisciplinary approach and modeling of a case of complex contamination in an Adriatic coastal aquifer
No full textThe understanding and the identification of processes which influence mobility, transport and degradation of contaminants in groundwater are determining factors that have to be considered in polluted sites management, in order to correctly plan their remediation.
This research deals with a case of complex contamination in central Adriatic Italy. The studied site is a residential area located on a coastal aquifer which is made up by sandy and silty sandy deposits up to 15 meters thick, laying on a plio-pleistocenic clayey aquiclude (Desiderio & Rusi, 2003). Here, groundwater is heavily polluted by metals (i.e. Fe, Mn e As), hydrocarbons and chlorinated solvents (i.e. PCE, TCE, DCEs, VC), due to several distinct pollution sources. As already known, the organic matter degradation, in this case related with an oil spill, triggers microbiological controlled redox processes in groundwater which involve redox-sensitive metallic species and chlorinated solvents (McCarty, 1997; Palmucci et al., 2016). In particular, the hydrocarbons degrades oxidising and acting as electron donors, while metallic species, as electron acceptors, are reduced and solubilised. Simultaneously, the chlorinated solvents degrades by mean of reductive dechlorination mechanism (i.e. from PCE to VC), acting as electron acceptors themselves. Nevertheless, since chlorinated solvents' reduction is not sometimes energetically favourable, heavily toxic by-products, as VC, can persist in groundwater. Thus, this dehalogenation process, when organic matter oxidises, competes with metallic species' reduction, complicating the dynamics which control the pollutants' diffusion in groundwater. In order to forecast the pollution's evolution in the aquifer, considering the hydrogeological framework, the numerical modeling of transport and hydrogeochemical processes has been implemented (Appelo & Postma, 2005), as a refinement and validation of the initial conceptual model. The dataset used in this study has been collected in 9 groundwater sampling rounds in the 2009-2014 period, soil samplings at different depths, and 2 hydraulic head measurement rounds. The monitoring network is made up by 43 points.
The preliminary results confirm the metals' mobilisation linked with hydrocarbon pollution. This process seems to be more favoured than the reductive dechlorination, considering the very high concentrations of VC in the aquifer
The landfill leachate impact on groundwater hydrogeochemistry in fine deposits: a multidisciplinary study
No full textThe leachate is one of the most important potential source of groundwater contamination (Kjeldsen et al., 2002), especially when the landfills are partially lined or unlined (Stefania et al., 2018).
The interaction between the leachate and the environmental media, in addition to spreading toxic compound in groundwater, leads to several hydrogeochemical and biological changes that, in turn, affect the natural conditions of aquifers (Christensen et al., 2001). These changes also involve compounds that are generally considered slightly or not polluting, such as the major ions (i.e. Na+, K+, Ca2+, Mg2+, Cl-, SO42-, HCO3-+CO32-), notwithstanding the Concentration Limits of Contamination (CLC) required by the current environmental legislation (i.e. D.Lgs. 152/06).
In this general framework, the main objective of this research is to get a deeper insight into these processes, related to the leachate/groundwater interaction, in a landfill site where the CLC exceedances are limited
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