1,721,060 research outputs found
Studies on water resources salinization along the Italian coast: 30 years of work|Studi sulla salinizzazione delle risorse idriche lungo le coste italiane: 30 anni di lavoro
No full textSpecial issue “focus on the salinization issue in the mediterranean area”
Get PDFThroughout the Mediterranean Region, recent and past studies have highlighted an increase in temperature, especially during summer, a decrease in precipitation and a change in the in-year precipitation pattern [...
Special issue: Denitrification in agricultural soils
Get PDFDenitrification, the main microbial reduction process of nitrate to the inert dinitrogen gas or to reactive gases such as nitric oxide and nitrous oxide [...
The issue of groundwater salinization in coastal areas of the mediterranean region: A review
Get PDFThe 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
Modelling present and future po river interactions with alluvial aquifers (Low Po River Plain, Italy)
No full textA modelling study on a multi-layered confined/unconfined alluvial aquifer system was performed to quantify surface water/groundwater interactions. The calibrated groundwater flow model was used to forecast climate change impacts by implementing the results of a downscaled A1B model ensemble for the Po river valley. The modelled area is located in the north-western portion of the Ferrara Province (Northern Italy), along the eastern bank of the Po river. The modelling procedure started with a large scale steady state model followed by a transient flow model for the central portion of the domain, where a telescopic mesh refinement was applied. The calibration performance of both models was satisfactory, in both drought and flooding conditions. Subsequently, forecasted rainfall, evapotranspiration and Po river stage at 2050, were implemented in the calibrated large scale groundwater flow model and their uncertainties discussed. Three scenarios were run on the large scale model: the first simulating mean hydrological conditions and the other two simulating one standard deviation above and below the mean hydrological conditions. The forecasted variations in groundwater/Po river fluxes are relevant, with a general increase of groundwater levels due to local conditions, although there are large uncertainties in the predicted variables
Modelling the salinization of a coastal lagoon-aquifer system
Get PDFIn 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
Denitrification in intrinsic and specific groundwater vulnerability assessment: A review
Get PDFSeveral groundwater vulnerability methodologies have been implemented throughout the years to face the increasing worldwide groundwater pollution, ranging from simple rating methodologies to complex numerical, statistical, and hybrid methods. Most of these methods have been used to evaluate groundwater vulnerability to nitrate, which is considered the major groundwater contaminant worldwide. Together with dilution, the degradation of nitrate via denitrification has been acknowledged as a process that can reduce reactive nitrogen mass loading rates in both deep and shallow aquifers. Thus, denitrification should be included in groundwater vulnerability studies and integrated into the various methodologies. This work reviewed the way in which denitrification has been considered within the vulnerability assessment methods and how it could increase the reliability of the overall results. Rating and statistical methods often disregard or indirectly incorpo-rate denitrification, while numerical models make use of kinetic reactions that are able to quantify the spatial and temporal variations of denitrification rates. Nevertheless, the rating methods are still the most utilized, due to their linear structures, especially in watershed studies. More efforts should be paid in future studies to implement, calibrate, and validate user-friendly vulnerability assessment methods that are able to deal with denitrification capacity and rates at large spatial and temporal scales
Limitations of GALDIT to map seawater intrusion vulnerability in a highly touristic coastal area
Get PDFCoastal 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
Natural and anthropogenic factors driving groundwater resources salinization for agriculture use in the Campania plains (Southern Italy)
Get PDFThe Mediterranean region is under pressure for a more sustainable use of water resources in view of the actual and future climate change. Under this pressure, the need to better assess the links between groundwater availability and quality and irrigated agriculture, is becoming urgent. Through the hydrogeologic and hydrochemical characterization of the coastal aquifers of a representative Mediterranean study area (the Campania Region in southern Italy), this study strengthened the analysis of basic components of the groundwater cycle and their temporal variability, including hydrologic, environmental and socio-economic aspects. Selected physiochemical properties of groundwater in 52 monitoring wells were considered from the Campania Environmental Protection Agency database. A total of 626 samples were collected from 2004 to 2018 to capture the water quality variability. Factor analysis and a specific groundwater quality index were also applied on 23 samples in two different timelines (2006, 2016) to capture the hydro-chemistry evolution through year. Moreover, land use and active pumping wells locations were used in the analysis. Spatial and temporal trends of base exchange indices (BEX) and sodium adsorption ratio (SAR) were computed along with Pearson coefficient among different variables, like well densities and distance from the coast. The variation in the distribution of salinity between 2006 and 2016, along with highly positive and highly negative BEX and groundwater quality index values, indicate unstable conditions for the future. In the greenhouse's areas, where groundwater exploitation is elevated, an increase of salinity was recorded due to seawater intrusion. In volcanic districts water rock interaction is the main driver of groundwater salinization, while mixing processes with carbonate freshwaters diminish groundwater salinities in the alluvial plains. This study demonstrates that groundwater over pumping can have a major impact on groundwater quality used for irrigation, despite the dominant influence that local geological and morphological features exert on the area
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