1,721,075 research outputs found
Special Issue “Salinization of Water Resources: Ongoing and Future Trends”
No full textAll over the Earth, more and more studies have shown the effects of climate changes generated by anthropic release of greenhouse gasses on the hydrological cycle [...
The issue of groundwater salinization in coastal areas of the mediterranean region: A review
Full text linkThe Mediterranean area is undergoing intensive demographic, social, cultural, economic, and environmental changes. This generates multiple environmental pressures such as increased demand for water resources, generation of pollution related to wastewater discharge, and land consumption. In the Mediterranean area, recent climate change studies forecast large impacts on the hydrologic cycle. Thus, in the next years, surface and ground-water resources will be gradually more stressed, especially in coastal areas. In this review paper, the historical and geographical distribution of peer-review studies and the main mechanisms that promote aquifer salinization in the Mediterranean area are critically discussed, providing the state of the art on topics such as actual saltwater wedge characterization, paleo-salinities in coastal areas, water-rock interactions, geophysical techniques aimed at delineating the areal and vertical extent of saltwater intrusion, management of groundwater overexploitation using numerical models and GIS mapping techniques for aquifer vulnerability to salinization. Each of the above-mentioned approaches has potential advantages and drawbacks; thus, the best tactic to tackle coastal aquifer management is to employ a combination of approaches. Finally, the number of studies focusing on predictions of climate change effects on coastal aquifers are growing but are still very limited and surely need further research
Direct measurement of dissolved dinitrogen to refine reactive modelling of denitrification in agricultural soils
No full textNitrogen fertilizers used in agriculture often cause nitrate leaching towards shallow groundwater, especially in lowland areas where soil permeability, ploughing, clay content, and the flat topography minimizes surface runoff. The introduction of good agricultural practices to reduce the nitrate amount entering the groundwater system is crucial to ameliorate the kinetic control on nitrate denitrification capacity. With this aim, a series of anaerobic mesocosms, consisting of loamy and clay soils and nitrate rich water, were modelled using acetate and natural organic matter as electron donors. Acetate was chosen because it is the main intermediate in many biodegradation pathways of organic compounds, and hence it is a suitable carbon source for denitrification. To account for the spatial variability of soil parameters, the experiments were performed in triplicates. The geochemical code PHREEQC(3) was used to simulate kinetic denitrification, and equilibrium reactions of gas and mineral phases. The reactive modelling results highlighted a rapid acetate and nitrate degradation rate, a rapid production of dissolved inorganic carbon and dinitrogen, and a steady concentration of dissolved iron and sulphate, suggesting that the main pathway of nitrate attenuation is through denitrification; concomitantly excluding the occurrence of other processes leading to nitrate consumption. In the absence of acetate, the loamy soil, poor of natural organic matter, did not allow to complete the denitrification process.This modelling study investigates in detail the relationship between the denitrification process in natural soils, with excess and in limitation of organic substrates, and the occurrence and fate of dissolved dinitrogen analysed with a high precision membrane inlet mass spectrometer. Results demonstrate that modelling nitrate degradation processes as a whole, using geochemical datasets and codes, will improve the estimates of agricultural landscapes denitrification and support better nitrogen management, especially in lowland environments. (C) 2018 Elsevier B.V. All rights reserved
Geochemical evolution and salinization of a coastal aquifer via seepage through peaty lenses
No full textThe aim of this study was to determine the role of buried peaty lenses in the salinization process of an unconfined coastal aquifer. To unravel the complex biogeochemical processes that occur between the peat matrix and the flowing through groundwater, two monitoring wells were sampled using high-resolution multilevel straddle packers. Moreover, to quantify the salt release in the aquifer from the peat lenses, a 1-m length column experiment was run for 62 days including a long equilibration step of 37 days, an elution step of 5 days, a stop flow of 15 days and a second elution step of 5 days. The column was monitored using 20 cm spaced ports to allow a precise reconstruction of the biogeochemical processes occurring within the matrix. A numerical model with SEAWAT-4.0 accounting for variable density flow and transport was used to simulate the observed salt concentration eluted from the column. To correctly reproduce the observed concentrations, a dual-domain approach coupled with a mass loading rate from the peat layer had to be accounted for. The results of this study highlight the capability of peat lenses to salinize the aquifer, to release large amount of sulfate and phosphate and to increase the chloride–bromide ratio
Modelling the salinization of a coastal lagoon-aquifer system
Full text linkIn this study, a coastal area constituted by alternations of saline-brackish lagoons and freshwater bodies was studied and modelled to understand the hydrological processes occurring between the lagoons, the groundwater system of the Po River Delta (Italy) and the Adriatic Sea. The contribution of both evaporation and anthropogenic factors on groundwater salinization was assessed by means of soil, groundwater and surface water monitoring. Highresolution multi-level samplers were used to capture salinity gradients within the aquifer and surface water bodies. Data were employed to calibrate a density-dependent numerical transport model implemented with SEAWAT code along a transect perpendicular to the coast line. The results show that the lagoon is hydraulically well connected with the aquifer, which provides the major source of salinity because of the upcoming of paleo-seawater from the aquitard laying at the base of the unconfined aquifer. On the contrary, the seawater (diluted by the freshwater river outflow) creates only a limited saltwater wedge. The increase in groundwater salinity could be of serious concern, especially for the pinewood located in the dune near the coast, sensitive to salinity increases. This case study represents an interesting paradigm for other similar environmental setting, where the assumption of classical aquifer salinization from a saltwater wedge intruding from the sea is often not representative of the actual aquifer's salinization mechanisms
Natural attenuation processes in the Corona Protocol: application to the “NIT” field site.
No full textThe paper is about the evaluation of natural attenuation at a petrochemical plant in Italy, contaminated by petroleum hydrocarbon
Interazione tra gli acquiferi A1 e A2 nella zona di Settepolesini (Bondeno) tramite simulazione numerica di flusso e trasporto.
No full textIl lavoro qui presentato ha come obiettivo lo studio idrogeologico del primo acquifero confinato A1 in un’area comprendente alcune porzioni delle province di Ferrara, Mantova e Bondeno.
La ricerca è stata possibile grazie al reperimento di dati provenienti dalle stratigrafie dei pozzi profondi esistenti e da studi precedenti effettuati dalla Regione Emilia Romagna, dalla Provincia di Ferrara, dal Comune di Bondeno e dalla ditta esercente la cava di Settepolesini presso Bondeno (FE). Dai dati e dalle misure raccolte si è cercato di ricavare e proporre un modello idrogeologico concettuale del sottosuolo che è poi sfociato in un modello numerico del flusso idrico sotterraneo (MODFLOW 2000). Inizialmente il grado di calibrazione di tale simulazione risultava scarso per cui sono state avanzate diverse ipotesi per cercare di migliorare il modello concettuale di riferimento. Una di queste ipotesi consisteva nel supporre la presenza di uno spartiacque piezometrico subparallelo al fiume Po dovuto alla coalescenza tra gli acquiferi A1 ed A2. Per testare tale ipotesi è stato quindi definito un piano di campionamento e di analisi che ha previsto il prelievo di campioni d’acqua presenti in 6 piezometri ubicati nell’area d’indagine. Sulla base dei dati idrogeochimici ottenuti è stato realizzato un modello numerico di trasporto non reattivo in regime stazionario, tramite il software MT3D-MS, che ha permesso di confermare la risalita di acque salate verso l’acquifero A1
Nitrogen and sulphur cycling in the saline coastal aquifer of Ferrara, Italy. A multi-isotope approach
No full textThe origin of high ammonium and sulphate concentrations, characterizing the saline groundwater of the
Po River floodplain coastal aquifer, are documented. A detailed understanding of the hydrogeochemical
conceptual model is built up using a hydrochemical (major ions, DOC, DIC and methane) and isotopic
(d15NNO3, d15NNH4, d18ONO3, d34SSO4, d18OSO4 and d13CDIC) approach. Based on previous hydrogeological
investigations, two boreholes located in contrasting environments (urban and agricultural) have been
sampled at high vertical resolution.
Groundwater is mostly under reducing conditions, characterized by high DOC and DIC concentrations
but low to moderate methane content. Dissolved ammonium, as high as 87.8 mgL1, derives by the
mineralization of N-organic rich fine sediments, as indicated by its N isotopic signatures (1÷3‰).
Attenuation processes of ammonium are ruled by dilution and by partial nitrification, supported by the
enrichment in d15NNH4 (~þ7‰). Apart from dilution/oxidation processes, the positive correlation between
d15NNO3 and d18ONO3 agreed with the occurrence of denitrification in the shallow part of the
aquifer. d34SSO4 and d18OSO4 data highlight that oxidation of pyrite occurs but is not necessarily linked to
nitrate removal. The isotope data showed that sulphate (>2500 mgL1) is of marine origin. In the deeper
part of the aquifer, sulphur and oxygen isotopes enrichment patterns, demonstrated that sulphate
reduction (SR) occurs in the aquifer and it is also possible that SR occurred in the underlying clay units.
d13CDIC pattern toward depleted d13CDIC values even as low as 40.4‰ documented the occurrence of SR
mediated by organic carbon and SR coupled to oxidation of methane (AOM) are involved in the sulphur
and carbon cycles. The present study shows the advantage of using stable isotopes complemented with
geochemical data to characterize the solutes' origins, both natural and anthropogenic, and giving insights
on biogeochemical transformations involving nitrogen, sulphur and carbon in coastal sediments
Limitations of GALDIT to map seawater intrusion vulnerability in a highly touristic coastal area
Full text linkCoastal aquifers are susceptible to seawater intrusion, especially touristic areas where the overexploitation combined with the agricultural use of groundwater represent a severe issue for water management. GALDIT methodology was applied as a management tool to identify and prevent salinization of the aquifer. GALDIT methodology needs six input parameters: groundwater occurrence (G), aquifer hydraulic conductivity (A), groundwater head above sea level (L), distance from the shore (D), impact of the existing status of seawater intrusion (I), and thickness of the aquifer (T). Then a contour map is created using three degree of vulnerability: high, medium and low. The higher vulnerability zone ranges from 40 to 550 m towards the mainland with the rest of the aquifer characterized by medium vulnerability. The main problem affecting the selected field site is the large water requirement during the summer period due to the touristic activities, but the correct use of surplus water collected in the winter can overcome this problem. This study demonstrates that further investigation on groundwater hydrochemistry and on water demand trends from the different activities impacting the field site should be implemented, in order to guarantee environmental and touristic development sustainability
Combined use of heat and saline tracer to estimate aquifer properties in a forced gradient test
No full textUsually electrolytic tracers are employed for subsurface characterization, but the interpretation of tracer test data collected by low cost techniques, such as electrical conductivity logging, can be biased by cation exchange reactions. To characterize the aquifer transport properties a saline and heat forced gradient test was employed. The field site, located near Ferrara (Northern Italy), is a well characterized site, which covers an area of 200 m2 and is equipped with a grid of 13 monitoring wells. A two-well (injection and pumping) system was employed to perform the forced gradient test and a straddle packer was installed in the injection well to avoid in-well artificial mixing. The contemporary continuous monitor of hydraulic head, electrical conductivity and temperature within the wells permitted to obtain a robust dataset, which was then used to accurately simulate injection conditions, to calibrate a 3D transient flow and transport model and to obtain aquifer properties at small scale. The transient groundwater flow and solute-heat transport model was built using SEAWAT. The result significance was further investigated by comparing the results with already published column experiments and a natural gradient tracer test performed in the same field. The test procedure shown here can provide a fast and low cost technique to characterize coarse grain aquifer properties, although some limitations can be highlighted, such as the small value of the dispersion coefficient compared to values obtained by natural gradient tracer test, or the fast depletion of heat signal due to high thermal diffusivity
- …
