1,721,040 research outputs found
Influence of Spill Pressure and Saturation on the Migration and Distribution of Diesel Oil Contaminant in Unconfined Aquifers Using Three-Dimensional Numerical Simulations
No full textSpilled hydrocarbons released from oil pipeline accidents can result in long-term environmental contamination and significant damage to habitats. In this regard, evaluating actions in response to vulnerability scenarios is fundamental to emergency management and groundwater integrity. To this end, understanding the trajectories and their influence on the various parameters and characteristics of the contaminant’s fate through accurate numerical simulations can aid in developing a rapid remediation strategy. This paper develops a numerical model using the CactusHydro code, which is based on a high-resolution shock-capturing (HRSC) conservative method that accurately follows sharp discontinuities and temporal dynamics for a three-phase fluid flow. We analyze nine different emergency scenarios that represent the breaking of a diesel oil onshore pipeline in a porous medium. These scenarios encompass conditions such as dry season rupture, rainfall-induced saturation, and varying pipeline failure pressures. The influence of the spilled oil pressure and water saturation in the unsaturated zone is analyzed by following the saturation contour profiles of the three-phase fluid flow. We follow with the high-accuracy formation of shock fronts of the advective part of the migration. Additionally, the mass distribution of the expelled contaminant along the porous medium during the emergency is analyzed and quantified for the various scenarios. The results obtained indicate that the aquifer contamination strongly depends on the pressure outflow in the vertical flow. For a fixed pressure value, as water saturation increases, the mass of contaminant decreases, while the contamination speed increases, allowing the contaminant to reach extended areas. This study suggests that, even for LNAPLs, the distribution of leaked oil depends strongly on the spill pressure. If the pressure reaches 20 atm at the time of pipeline failure, then contamination may extend as deep as two meters below the water table. Additionally, different seasonal conditions can influence the spread of contaminants. This insight could directly inform guidelines and remediation measures for spill accidents. The CactusHydro code is a valuable tool for such applications
High-resolution shock-capturing numerical simulations of three-phase immiscible fluids from the unsaturated to the saturated zone
Full text linkNumerical modeling of immiscible contaminant fluid flow in unsaturated and saturated porous aquifers is of great importance in many scientific fields to properly manage groundwater resources. We present a high-resolution numerical model that simulates three-phase immiscible fluid flow in both unsaturated and saturated zone in a porous aquifer. We use coupled conserved mass equations for each phase and study the dynamics of a multiphase fluid flow as a function of saturation, capillary pressure, permeability, and porosity of the different phases, initial and boundary conditions. To deal with the sharp front originated from the partial differential equations’ nonlinearity and accurately propagate the sharp front of the fluid component, we use a high-resolution shock-capturing method to treat discontinuities due to capillary pressure and permeabilities that depend on the saturation of the three different phases. The main approach to the problem’s numerical solution is based on (full) explicit evolution of the discretized (in-space) variables. Since explicit methods require the time step to be sufficiently small, this condition is very restrictive, particularly for long-time integrations. With the increased computational speed and capacity of today’s multicore computer, it is possible to simulate in detail contaminants’ fate flow using high-performance computing
Investigating the migration of immiscible contaminant fluid flow in homogeneous and heterogeneous aquifers with high-precision numerical simulations
Full text linkNumerical modeling of the migration of three-phase immiscible fluid flow in variably saturated zones is challenging due to the different behavior of the system between unsaturated and saturated zones. This behavior results in the use of different numerical methods for the numerical simulation of the fluid flow depending on whether it is in the unsaturated or saturated zones. This paper shows that using a high-resolution shock-capturing conservative method to resolve the nonlinear governing coupled partial differential equations of a three-phase immiscible fluid flow allows the numerical simulation of the system through both zones providing a unitary vision (and resolution) of the migration of an immiscible contaminant problem within a porous medium. In particular, using different initial scenarios (including impermeable “lenses” in heterogeneous aquifers), three-dimensional numerical simulation results are presented on the temporal evolution of the contaminant migration following the saturation profiles of the three-phases fluids flow in variably saturated zones. It is considered either light nonaqueous phase liquid with a density less than the water, or dense nonaqueous phase liquid, which has densities greater than the water initially released in unsaturated dry soil. Our study shows that the fate of the migration of immiscible contaminants in variably saturated zones can be accurately described, using a unique mathematical conservative model, with different evolution depending on the value of the system’s physical parameters, including the contaminant density, and accurately tracking the evolution of the sharp (shock) contaminant front
Sui criteri di scelta delle risorse idriche integrative, sostitutive e di emergenza in Campania
No full textThe Water–Energy–Food Nexus in European Countries: A Review and Future Perspectives
No full textThe interaction between water, energy, and food as the water–energy–food (WEF) nexus has drawn much attention recently to solve upcoming uncertainty in food security. The aim of this study is to investigate the status of the WEF nexus in European countries. It is indicated that the largest nexus studies (among 27 European countries) have been conducted in Spain and Italy. It is confirmed that there is a large number of nexus studies in water-stressed countries while there are few studies on water-abundant countries (Slovakia and Luxembourg). Based on existing research, the majority of nexus studies focused on energy production. It is highlighted that most of the nexus studies were focused on water quantity aspects (rarely related to quality aspects) and energy; however, other resources including land, climate, ecosystem, soil, and environment received little attention. The migration of people as a result of climate change in the WEF nexus is not considered. Moreover, there is a lack of common and standard frameworks for nexus assessment. Therefore, we suggest a standard approach for nexus studies and produce a cross-sectoral and holistic approach for the evaluation of a water (quantity and quality)–energy–food–land–climate (WqEFLC) nexus that takes into consideration the circular economy
The Ecotoxicity Approach as a Tool for Assessing Vermiremediation Effectiveness in Polychlorobiphenyls, Polychlorodibenzo-p-Dioxins and Furans Contaminated Soils
Full text linkChemical analyses are inadequate for assessing soil biological quality. Instead, the soil living community can be used both for monitoring and restoring soil health. The aim of this research was to verify vermiremediation efficiency in PCDD/F and PCB contaminated soils from Brescia-Caffaro (Italy), using an ecotoxicity approach. To gauge whether Caffaro soil could sustain a living community, a characterization of the arthropod community was conducted. Earthworms’ suitability for soil bioremediation was assessed applying ecotoxicity tests. Five treatments were set up: 1) contaminated soil; 2) contaminated soil + Eisenia fetida; 3) contaminated soil + Lepidium sativum; 4) contaminated soil + E. fetida + L. sativum, 5) uncontaminated soil + E. fetida. The ecotoxicity tests were: L. sativum germination index and root elongation inhibition, and Folsomia candida survival and reproduction, applied on soil and elutriate on: starter soil (T0), after 56 and 112 days (T56 and T112), the last after water percolation. Soil arthropod community was dominated by Hypogastruridae, Oribatida and, to a lesser degree, Formicidae and Coleoptera larvae. Ecotoxicity tests showed that F. candida reproduction and L. sativum root elongation were more adversely affected by pollutants than survival and germination. The higher soil ecotoxicity at T112 than at T56, suggested higher contaminant bioavailability after water addition. F. candida showed more variability between soil and elutriate than L. sativum. Both bioassays suggested earthworm treatment as the most promising. The importance of selecting different organisms in soil ecotoxicity monitoring, and the role of elutriate like a solid phase complement, was highlighted
Unusual behavior of epikarst in Acqua dei Faggi carbonate aquifer (Southern Italy)
No full textHydrogeological and geophysical investigations demonstrated the existence of an epikarstic zone in a carbonate aquifer of Southern Italy, about 10 m thick. Nevertheless, the hydrogeological behaviour of the epikarst is different from that schematized by several authors. In the test site, the contrast in permeability at the bottom of the epikarst does not cause retention of percolation and storage of water in a perched temporary aquifer within the uppermost portion of the carbonate medium. Because of the high fracture density and good interconnection of openings within the underlying limestone, the percolation is diffuse also below the epikarstic zone, as well as the groundwater flow. The 'funnelling' effect into larger shafts does not play an important role on the hydrogeological behaviour of the aquifer
CAN’T TELL A BOOK BY ITS COVER: DISJOINTED GROUNDWATER CONTAMINATION AND LAND USE IN AN ALLUVIAL AQUIFER OF NORTHERN ITALY
No full textIn the Po plain, intensive agriculture is supported by large irrigation volumes and use of fertilizers. We analysed the effects of different land uses in a sector of the Mincio River on groundwater hydrochemical characteristics and hypothesized local regulation of NO3- contamination. In the unconfined coarse-grained alluvial aquifer, hydraulic heads were measured monthly in 17 wells from May 2019 to December 2019, to trace how the aquifer recharge and manure spreading influence groundwater physico-chemical parameters and quantity. The experimental site was divided into two different zones on the left and right bank characterized by different land use. Although these dissimilarities concern different irrigation and fertilization practices, we measured in both areas nitrate (NO3-) contamination in groundwater, with concentrations exceeding legislative limits by a factor of 2. Our results suggest that NO3- contamination in this area is not only driven by specific land use and related agricultural practice; rather, other local factors intrinsic to the local aquifer and groundwater characteristics play an important role. Presented results on groundwater quality and quantity provide useful information to increase knowledge on local N dynamics and to the administrations regulating fertilizer use in this area, already reported as Nitrate Vulnerable Zones (NVZ)
Environmental impact of cattle grazing on a karst aquifer in the southern Apennines (Italy): quantification through the grey water footprint
No full textIn this paper we draw on a unique dataset of hydrological and microbiological time series to apply water footprint (WF) methodology to quantify the environmental impact of cattle grazing on karst area in a regional park of the southern Apennines (Italy). The use of WF methodology in the same specific environment where relevant data are monitored, and the hydrogeological and microbiological characterisation of the study area, validate the results of our WF assessment, that can be summarised as follows. First, we show that an ecological indicator such as the grey water footprint (GWF) may be of particular relevance to the park authority to implement policies to preserve groundwater quality. Second, we introduce a new metric, referred to as the environment-related grey water footprint (GWFenv), to estimate the virtual water needed to absorb the microbial pollution of a cattle grazing process
Estimation of recharge in mountain hard-rock aquifers based on discrete spring discharge monitoring during base-flow recession
Full text linkEstimation of aquifer recharge is key to effective groundwater management and protection. In mountain hard-rock aquifers, the average annual discharge of a spring generally reflects the vertical aquifer recharge over the spring catchment. However, the determination of average annual spring discharge requires expensive and challenging field monitoring. A power-law correlation was previously reported in the literature that would allow quantification of the average annual spring discharge starting from only a few discharge measurements in the low-flow season, in a dry summer climate. The correlation is based upon the Maillet model and was previously derived by a 10-year monitoring program of discharge from springs and streams in hard-rock aquifers composed of siliciclastic and calcareous turbidites that did not have well defined hydrogeologic boundaries. In this research, the same correlation was applied to two ophiolitic (peridotitic) hard-rock aquifers in the Northern Apennines (Northern Italy) with well-defined hydrogeologic boundaries and base-outflow springs. The correlation provided a reliable estimate of the average annual spring discharge thus confirming its effectiveness regardless of bedrock lithology. In the two aquifers studied, the measurable annual outputs (i.e. sum of average annual spring discharges) could be assumed equal to the annual inputs (i.e. vertical recharge) based on the clear-cut aquifer boundaries and a quick groundwater circulation inferable from spring water parameters. Thus, in such setting, the aforementioned correlation also provided an estimate of the annual aquifer recharge allowing the assessment of coefficients of infiltration (i.e. ratio between aquifer recharge and total precipitation) ranging between 10 and 20%
- …
