174 research outputs found
Freshwater-seawater mixing experiments in sand columns
No full textA study was performed on vertical mixing between freshwater and seawater in controlled column experiments. The aim was to quantify the variation in the thickness of the mixing zone caused by water table fluctuations in aeolian dune sandy sediments. A series of column experiments were setup: first a study on in-well mixing was completed to understand the suitability of down-hole logging in existing piezometers versus multi level sampling; then, an unsaturated-saturated column experiment with sandy aeolian dune sediments of the target aquifer was performed to characterize the mixing zone thickness; finally the third column experiment was conducted by imposing a groundwater fluctuation of 0.1. m to quantify the increase of the freshwater-saltwater mixing zone due to vertical water table oscillations. The freshwater-saltwater mixing zone increase was very limited and did not exceed 0.1. m. All experiments were modeled by means of the SEAWAT numerical code, and calibrated against saltwater concentrations. The model fit was good for all experiments, providing insights into the vertical dispersivity of sandy aeolian dune sediments and also into the reliability and precision of the freshwater-saltwater interface monitoring methods. The down-hole logging technique, in fact, was demonstrated to be inefficient when horizontal flow velocity is negligible; in this case only multi-level sampling techniques provided reliable results. © 2012 Elsevier B.V.
Special issue “focus on the salinization issue in the mediterranean area”
No full textThroughout 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 [...
Arsenic speciation in a contaminated coastal aquifer below a former fertilizer production plant
No full textInorganic arsenic has been widely used during
the production cycle of fertilizers and pesticides
and leakage into sub-soils and shallow
groundwater has been reported in the recent
literature (Root et al. 2009; Cancés et al. 2005).
Despite of this, most of the scientific papers has
been focused on natural arsenic mobilization
and geochemical cycling in the subsurface
(Hering J. G. and Kneebone 2002; Lin and Puls
2003). Thus, more studies are still needed to
understand the mobilization/immobilization
mechanisms of arsenic in highly contaminated
sites. Since the arsenic mobilization is usually
driven by redox processes, pH changes and
ionic strength of the solutions (Smedley and
Kinniburgh 2002), it is foremost important to
study its behavior in coastal aquifers where all of
these factors essentially coincide. In fact, like for
the surface waters, the groundwater mixing zone
can affect the biogeochemical cycling of metals
and nutrients, which are sensitive to changes in
salinity and redox potential (Slomp et al. 2004).
The study site is a former fertilizer plant located
near the shore line, in Italy. The overall
groundwater geochemistry at the study site has
been documented in a previous paper
(Mastrocicco et al. 2011). Within this framework,
a detailed characterization of arsenic in
groundwater was performed to elucidate the
mobilization/immobilization mechanisms actually
occurring at the site
Special issue: Denitrification in agricultural soils
No full textDenitrification, the main microbial reduction process of nitrate to the inert dinitrogen gas or to reactive gases such as nitric oxide and nitrous oxide [...
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 textGEO.POWER project: low-enthalpy geothermal energy performance and long-term strategies for Ground-Coupled Heat Pumps (GCHP) in residential and industrial building.
No full textThe general objective of GEO.POWER project is to exchange best practices related to low enthalpy energy supply and - after a technical and cost/benefit assessment to evaluate the potential of reproducibility - to prepare action plans for the large scale introduction of Ground-Coupled Heat Pumps (GCHP) in each of the member regions. Each action plan needs to provide an organized set of legal/regulatory, economic and technical proposals to address long-term investments strategy for GCHP application at wide scale. The partnership, coordinated by the Province of Ferrara (Italy) is composed by Ministries, Regions, Local Authorities, Universities and R&D agencies of 9 countries (Bulgaria, Hungary, Greece, Italy, Sweden, Estonia, UK, Belgium and Slovenia) that are dealing at different level with the attainment of European policy objectives in relation to 20/20/20 Kyoto targets and the EU Building Performance Directive
Large tank experiment on nitrate fate and transport: the role of permeability distribution
No full textA long-term elution experiment to study the saturated transport of pre-accumulated fertilizers by-products, was conducted within a large tank (4 x 8 x 1.4 m) equipped with 26 standard piezometers. Sandy sediments (35 m(3)), used to fill the tank, were excavated from an unconfined alluvial aquifer near Ferrara (Northern Italy); the field site was connected to a pit lake located in a former agricultural field. To evaluate spatial heterogeneity, the tank's filling material was characterized via slug tests and grain-size distribution analysis. The investigated sediments were characterized by a large spectrum of textures and a heterogeneous hydraulic conductivity (k) field. Initial tank pore water composition exhibited high concentration of nitrate (NO(3) (-)) sulfate (SO(4) (2-)) calcium (Ca(2+)), and magnesium (Mg(2+)), due to fertilizer leaching from the top soil in the field site. The initial spatial distribution of NO(3) (-) and SO(4) (2-) was heterogeneous and not related to the finer grain-size content (< 63 mu m). The tank's material was flushed with purified tap water for 800 days in steady-state conditions; out flowing water was regularly sampled to monitor the migration rate of fertilizer by-products. Complete removal of NO(3) (-) and SO(4) (2-) took 500 and 600 days, respectively. Results emphasized organic substrate availability and spatial heterogeneities as the most important constraints to denitrification and nitrogen removal, which increase the time required to achieve remediation targets. Finally, the obtained clean-up time was compared with a previous column experiment filled with the same 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
Misleading reconstruction of seawater intrusion via integral depth sampling
No full textSaltwater intrusion in coastal aquifers is an urgent issue for the actual and future groundwater supply and a detailed characterization of groundwater quality with depth is a fundamental prerequisite to correctly distinguish salinization processes. In this study, interpolated Cl- maps of the Po River delta coastal aquifer (Italy), gained with Integrated Depth Sampling (IDS) and Multi-Level Sampling (MLS) techniques, are compared. The data set used to build up the IDS and MLS interpolated Cl- maps come from numerous monitoring campaigns on surface and ground waters, covering the time frame from 2010 to 2014. The IDS interpolated Cl- map recalls the phenomenon of actual seawater intrusion, with Cl- concentration never exceeding that of seawater and the absence of hypersaline groundwater all over the study area. On the contrary, in the MLS interpolated Cl- maps the lower portion of the unconfined aquifer presents hypersaline groundwater making it necessary to consider salinization processes other than actual seawater intrusion, like upward flux from a saline aquitard. Results demonstrate the obligation of using MLS in reconstructing a reliable representation of the distribution of salinity, especially in areas where the density contrast between fresh and saline groundwater is large. Implications of the reported field case are not limited to the local situation but have a wider significance, since the IDS technique is often employed in saltwater intrusion monitoring even in recent works, with detrimental effect on the sustainable water resource management of coastal aquifers
Reactive modelling of 1,2-DCA and DOC near the shoreline. Journal of Contaminant Hydrology
No full text1,2-Dichloroethane (1,2-DCA) was found to be the most abundant compound among chlorinated hydrocarbons detected in a petrochemical plant in southern Italy. This site is located near the
coastline, and it is set above an unconfined coastal aquifer, where seawater intrusion is present.
The presence of organic and inorganic contaminants at this site has required the implementation of remediation strategies, consisting of pumping wells (hydraulic barrier) and a horizontal flow barrier. The purpose of this work was to assess the influence of salt water intrusion on the degradation rate of 1,2-DCA. This was done on a three-dimensional domain relative to a limited
portion of a well characterized field site, accounting for density-dependent flow and reactive transport modelling of 1,2-DCA and Dissolved Organic Carbon (DOC). The modelling procedure
was performed employing SEAWAT-4.0 and PHT3D, to reproduce the complex three-dimensional flow and transport domain. In order to determine the fate of 1,2-DCA, detailed field investigations provided intensive depth profile information. Different, kinetically controlled degradation rates were simulated to explain the observed, selective degradation of pollutants in groundwater.
Calibration of the model was accomplished by comparison with the two different sets of measurements obtained from the MLS devices and from pumping wells. With the calibrated model, it was possible to distinguish between dispersive non-reactive processes and bacterially mediated reactions. In the non-reactive model, 1,2-DCA sorption was simulated using linear sorption coefficient determined with field data and 1,2-DCA degradation was simulated using a first order decay coefficient using literature data as initial guess. Finally, on the reactive transport
model, where a two-step approach with partial equilibrium approach was implemented, the effects of neglecting the cation exchange capacity, omitting density-dependent flow, and refining
the vertical discretization of the model were investigated. Comparison of results from various scenarios shows that geochemical changes in inorganic constituents can be used to improve the site's conceptual model, and establishes that natural degradation processes can be suitable for 1,2- DCA as a remediation option
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