385 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 [...
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
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
Modelling the salinization of a coastal lagoon-aquifer system
No full textIn 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
Monitoring and Modeling Nitrate Persistence in a Shallow Aquifer
No full textA modeling study on fertilizer by-products fate and transport was performed in an unconfined shallow aquifer equipped with a grid of 13 piezometers. The field site was located in a former agricultural field overlying a river paleochannel near Ferrara (Northern Italy), cultivated with cereals rotation until 2004 and then converted to park. Piezometers were installed in June 2007 and were monitored until June 2009 via pressure transducer data loggers to evaluate the temporal and spatial variation of groundwater heads, while an onsite meteorological station provided data for recharge rate calculations via unsaturated zone modeling. The groundwater composition in June 2007 exhibited elevated nitrate (NO 3- ) and chloride (Cl-) concentrations due to fertilizer leaching from the top soil. The spatial distribution of NO 3- and Cl- was heterogeneous and the concentration decreased during the monitoring period, with NO 3- attenuation (below 10 mg/l) after 650 days. A transient groundwater flow and contaminant transport model was calibrated versus observed heads and NO 3- and Cl- concentrations. Cl- was used as environmental tracer to quantify groundwater flow velocity and it was simulated as a conservative species. NO 3- was treated as a reactive species and denitrification was simulated with a first order degradation rate constant. Model calibration gave a low denitrification rate (2.5e-3 mg-NO 3- /l/d) likely because of prevailing oxic conditions and low concentration of dissolved organic carbon. Scenario modeling was implemented with steady state and variable flow time discretization to identify the mechanism of NO 3- attenuation. It was shown that transient piezometric conditions did not exert a strong control on NO 3- clean up time, while transient recharge rate did, because it is the main source of unpolluted water in the domain. © 2010 Springer Science+Business Media B.V
The issue of groundwater salinization in coastal areas of the mediterranean region: A review
No full textThe 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
Colombani, O. Paysans du Brésil. 1987
No full textLerat Serge. Colombani, O. Paysans du Brésil. 1987. In: Cahiers d'outre-mer. N° 164 - 41e année, Octobre-décembre 1988. p. 431
H. Giaufret-Colombani, Rhétorique de Jules Vallès
No full textBellet Roger. H. Giaufret-Colombani, Rhétorique de Jules Vallès. In: Romantisme, 1985, n°49. L'imaginaire du romantisme anglais. pp. 126-127
Trend of Heavy Metal Release According to Forecasted Climate Change in the Po Delta
No full textThe low-lying coastal areas, and especially the delta areas are prone to saltwater intrusion due to sea level rise, which may lead to a loss of ecosystem services brought about by salinization of already limited freshwater reserves. Despite the acknowledged importance of climate change impacts and land use practices on water resources availability, there is still a lack of studies on the issue of climate change induced alteration of water quality. To understand the hydrogeochemical processes occurring within the shallow groundwater system of the Po River delta (Italy), the contribution of local water-sediment interaction and the anthropogenic influence on groundwater quality were quantified. High-resolution multi-level sampling was used to capture chemical gradients within the aquifer. Data were employed to calibrate a density-dependent multicomponent reactive transport model implemented with PHT3D code along a flow line. The reactive network accounted for redox driven organic matter oxidation and cation exchange. Finally, a series of numerical scenarios were run following the projection of IPCC 2014 on sea level rise and climate change. Results of the predictive model highlight an increase of arsenic and lead in the shallow portion of the aquifer, drained by the reclamation network. The increase of heavy metals export toward surface waters could be of serious concern, since the drainage network operates also for irrigation purposes. Thus, the surface water quality could be negatively affected by climate change
Seismic induced variation of hydraulic conductivity distribution in a large tank
No full textA large tank (4x8x1.4 m) equipped with 26 standard piezometers and filled with sandy sediments (35 m3), was characterized via slug tests and grain size distribution analysis in 2006. The characterization via slug tests was repeated in 2013 after the seismic events of May 2012 near Ferrara (IT) characterized by a maximum Mw of 5.9 to infer the hydrological response of the tank's hydraulic conductivity field to the stresses induced by the earthquake. Results show a general decrease in hydraulic conductivity values, due to compaction phenomena, and a variation in the spatial distribution of hydraulic conductivity values, directly correlated to the presence of the finer fraction of the sediments within the large tank. In particular, the lenses, prevalently made of sandy sediments showed a negligible reduction, while the lenses constituted prevalently by silt displayed a larger decrease. The differential hydraulic conductivity reduction inhibited the flow linkages between the sandy lenses, provoking a four times decrease in the bulk hydraulic conductivity of the tank. This laboratory experiment highlights that pronounced hydraulic conductivity shrinkages should be expected after important seismic events in heterogeneous fine alluvial units
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