Characterization of the lowland coastal aquifer of Comacchio (Ferrara, Italy): Hydrology, hydrochemistry and evolution of the system
Introduction
The recognition of groundwater salinization origin in coastal aquifers is not straightforward; in many cases it is reasonable just to presume the involvement of present seawater. Though, besides present seawater, groundwater salinization can result from other natural salt sources or from human activities (Cartwright et al., 2004, Custodio, 1997, Fakir et al., 2002, Richter and Kreitler, 1993, Sanchez-Martos et al., 2002, Stuyfzand and Stuurman, 1994, Tellam, 1995, Tulipano et al., 2005). The most relevant salt sources/processes recognized worldwide are: evaporation, evaporite leaching, mobilization of salts stored in the unsaturated zone, infiltration of non-marine polluted surface waters, slow-moving saline/salt waters of marine origin (Barbecot et al., 2000, Darling et al., 1997, Fidelibus and Tulipano, 1996, Ng and Jones, 1995), highly mineralized waters from geothermal fields (Fidelibus et al., 2011a), sea spray, hyper-filtration, agricultural practices (return flow, use of fertilizers and irrigation with treated wastewater), cycling wetting and drying. Mixing processes with present seawater and/or saline ground waters are normally enhanced by human actions as over-exploitation (causing lateral seawater intrusion and/or upconing), presence of drainage systems for land reclamation, and construction of navigation channels along rivers or artificial canals (Barlow and Reichard, 2010, Custodio, 2010, Fidelibus et al., 2011b, Kass et al., 2005). In addition, has been recently demonstrated the importance of characterizing vertical variability of aquifer properties for quantifying the magnitude and direction of upward seepage of saline groundwater (de Louw et al., 2010, de Louw et al., 2011).
Whatever the salt source, its recognition is very often masked by the activation of water–rock interactions directly related to increase in water ionic strength, whose effects overlap those ones caused by the salt source. The salt sources have different geochemical and isotopic imprints. Thus, an approach by multiple natural tracers is required for their recognition: the chemical composition of present seawater is used in this case as the end-member of non-reactive freshwater–saltwater mixing for deducing overlapping/triggered water–rock interactions and solute contribution (de Montety et al., 2008, Fidelibus and Tulipano, 1996, Ghiglieri et al., 2009, Giménez and Morell, 1997, Howard and Lloyd, 1983, Yamanaka and Kumagai, 2006).
The Geological Survey of the Emilia-Romagna Region (Northern Italy) has developed a regional monitoring network to monitor saltwater intrusion in the coastal aquifer facing Adriatic Sea (Bonzi et al., 2010). Through the hydrogeologic and hydrochemical characterization of the coastal aquifer, this study, aims at identifying the origin and the mechanism of groundwater salinization, to the ultimate goal of the prevention or mitigation of groundwater resources deterioration, and the promotion of a sustainable water resource management.
Section snippets
Study area
The study area is located in the coastal floodplain of the Po River, in Northern Italy (Fig. 1). This area is characterized by intensive agriculture inland and intensive tourism along the coast during summer periods (June–September). Most of the territory is a recently reclaimed land with flat topography below sea level, and with an altitude ranging from 5 to −11 m above sea level (a.s.l.); the only topographic heights consist of dune systems, paleodunes and river banks.
The surface hydrographic
Materials and methods
This study combines field data collected during two different campaigns (June and November 2011). This section describes the methodology used to characterize the selected transect, in particular the methodology developed via straddle low pressure packers to characterize simultaneously vertical hydraulic gradients, permeability, and groundwater quality with the aim of identifying the aquifer dynamics and the spatial distribution and composition of saline groundwater.
Hydrostratigraphycal characterization
Grain size distribution analysis carried out along the transect reveals the presence of an heterogonous aquifer with very poorly sorted silty clay and peat lenses overlaying a highly permeable well sorted sandy layer typical of high energy depositional environments, such as coastal environment, intercalated with poorly sorted sandy silt lenses. Porosity values range between 19% and 76% with an average value of 30%; the highest values of porosity are associated with the presence of peat layers,
Conclusions
This study contributes to the knowledge of the hydrology, hydrochemistry and evolution of the coastal aquifer of Comacchio (Ferrara, Italy) by shedding lights on the main process of groundwater salinization in this area.
The hydrogeological and hydro-geochemical investigations carried out along the selected transect allow identifying the role of seepage and water–sediment interactions in the aquifer salinization process and in the modification of groundwater chemistry.
The results suggest that
Acknowledgements
We gratefully thank Paolo Severi and Lorenzo Calabrese from the Geological, Seismic and Soil Survey of Emilia-Romagna Region for their technical and scientific support. Enzo Salemi and Davide Rizzati from the University of Ferrara are thanked for their help in the field and laboratory activities.
References (72)
- et al.
Using the Cl/Br ratio as a tracer to identify the origin of salinity in aquifers in Spain and Portugal
J. Hydrol.
(2008) - et al.
Geochemical and mineralogical variations as indicators of provenance changes in Late Quaternary deposits of SE Po Plain
Sediment. Geol.
(2002) - et al.
Geochemical processes and solute transport at the seawater/freshwater interface of a sandy aquifer
Geochem. Cosmochim. Acta
(2005) - et al.
Barometric pressure influence on water table fluctuations in coastal aquifers of partially enclosed seas: an example from the Adriatic coast, Italy
J. Hydrol.
(2011) - et al.
Hydrochemical and isotopic characterisation of the Bathonian and Bajocian coastal aquifer of the Caen area (northern France)
Appl. Geochem.
(2000) - et al.
Processes affecting groundwater chemistry in a zone of saline intrusion into an urban sandstone aquifer
Appl. Geochem.
(1998) - et al.
Saline intrusion and refreshening in a multilayer coastal aquifer in the Catania Plain (Sicily, Southern Italy): dynamics of degradation processes according to the hydrochemical characteristics of groundwater
J. Hydrol.
(2005) - et al.
Hydrogeochemical and isotopic constrains on the origins of dryland salinity, Murray basin, Victoria, Australia
Appl. Geochem.
(2004) - et al.
Isotopic evidence for paleowaters in the British Isles
Appl. Geochem.
(1997) - et al.
Chlorine-36, bromide, and the origin of spring water
Chem. Geol.
(2001)
Upward groundwater flow in boils as the dominant mechanism of salinization in deep polders
J. Hydrol.
Origin of groundwater salinity and hydrogeochemical processes in a confined coastal aquifer: case of the Rhône delta (Southern France)
Appl. Geochem.
Cl/Br ratios of Lake Kinneret, pore water and associated springs
J. Hydrol.
Human-induced hydrogeological changes and sinkholes in the coastal gypsum karst of Lesina Marina area (Foggia Province, Italy)
Eng. Geol.
Estimation of long-term diffuse groundwater discharge in the northern Sahara using stable isotope profiles in soil water
J. Hydrol.
Isotopic and geochemical characterization of salinization in the shallow aquifers of a reclaimed subsiding zone: the southern Venice Lagoon coastland
J. Hydrol.
Saltwater intrusion in the unconfined coastal aquifer of Ravenna (Italy): a numerical model
J. Hydrol.
Gypsum precipitation/dissolution as an explanation of the decrease of sulphate concentration during seawater intrusion
J. Hydrol.
Chloride/bromide ratios in leachate derived from farm-animal waste
Environ. Pollut.
The impact of freshwater and wastewater irrigation on the chemistry of shallow groundwater: a case study from the Israeli Coastal Aquifer
J. Hydrol.
What information can we get from pumping tests?-comparing pumping test configurations using sensitivity coefficients
J. Hydrol.
Hydrogeochemistry of Grand Cayman, British West Indies: implications for carbonate diagenetic studies
J. Hydrol.
Regional hydrochemical study on salinization of coastal aquifers, western coastal area of South Korea
J. Hydrol.
Identification of the origin of salinization in groundwater using minor ions (Lower Andarax, Southeast Spain)
Sci. Total Environ.
A review of the Delta Po evolution (Italy) related to climatic changes and human impacts
Geomorphology
The interplay of eustasy, climate and human activity in the late Quaternary depositional evolution and sedimentary archietecture of the Po Delta system
Mar. Geol.
Hydrochemistry of the saline groundwaters of the Lower Mersey Basin Permo-Triassic sandstone aquifer, UK
J. Hydrol.
Combining pedotransfer functions with physical measurements to improve the estimation of soil hydraulic properties
Geoderma
Groundwater chemistry patterns in the phreatic aquifer of the central Belgian coastal plain
Appl. Geochem.
Sulfur isotope constraint on the provenance of salinity in a confined aquifer system of the southwestern Nobi Plain, central Japan
J. Hydrol.
Impacts of agricultural practices on soil and water quality in the Mediterranean region and proposed assessment methodology
Agric. Ecosyst. Environ.
Holocene forest pollen vegetation of the Po Plain, northern Italy
Allionia
Facies architecture and latest Pleistocene-Holocene depositional history of the Po Delta (Comacchio Area), Italy
J. Geol.
Use of bromide/chloride ratios to differentiate potential sources of chloride in a shallow, unconfined aquifer affected by brackish-water intrusion
Hydrogeol. J.
Salt water intrusion in the coastal aquifer of the southern Po Plain, Italy
Hydrogeol. J.
Geochemistry, Groundwater and Pollution
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