1,721,030 research outputs found
Salt Water Contamination On Venice lagoon Mainland: New Evaluation Of Origin, Extension And Dynamics
No full textThe Venice Lagoon mainland is affected by salt water contamination in coastal and circum-lagoonal aquifers due to the close vicinity of both the sea and lagoon. The territory, characterized lithologically by alternating layers of silt, clay and sand which have marine, continental and/or marsh origins, is characterized by several critical conditions. These include the existence of paleorivers, lagoonal paleochannels, and rivers which are artificially suspended above the surrounding land by dikes. All of these conditions contribute to an increase in groundwater salinization. Areas with high permeability seem to constitute a preferential way of movement for salt water from the sea or lagoon towards the mainland. Old fossil water seems to be able to reach the surface and contribute to an increase in the process of salt pollution. In fact, during the 1970s, several studies had detected, throughout the territory, the existence of a deep salt water aquifer storing fossil saline water. This aquifer lies at a depth of about 300-450 m in the southern part of the study area and of more than 600 m in the northern part of the Venice mainland. Salt water contamination of subsoil could cause ground salinization and, consequently, desertification of the area, with great economical consequences. These include damaging the large agricultural development of the territory as well as having adverse impacts on the tourist industry.
The combined use of adequately validated geophysical and geochemical tools confers a multidisciplinary character to the research and allows for the definition of the phenomenon’s superficial extension. Geophysical analysis based on Vertical Electrical Sounding (VES) and conductivity logs have been performed together with water table measurements and geochemical analysis on samples collected from selected wells. Moreover, a critical review of old geophysical data allowed for the verification of possible saline contamination changes in time.
Interesting results have been obtained within the northern sector of the Venice lagoon mainland, specifically within territory of Jesolo. In this case, considering the influence of the Piave and Sile rivers and the presence of a coastal sand dune, it is possible to create a map of salt water contamination to evaluate the agricultural use of superficial water.
Therefore, the aim of this research is to define the effective origin of salt water found in the aquifers of the northern lagoon mainland, its distribution, extension and its preferential way of movement within the territory. Thereby, relating all the information acquired to the geological, geomorphological and stratigraphic characteristics of the area
Soil thermal behavior in different moisture condition: an overview of ITER project from laboratory to field test monitoring
No full textThe thermal properties of soils can be considered one of the most important parameters for many engineering projects designing. In detail, the thermal conductivity plays a fundamental role when dimensioning ground heat exchangers, especially very shallow geothermal (VGS) systems, interesting the first 2 m of depth from the ground level. However, the determination of heat transfer in soils is difficult to estimate, because depends on several factors, including, among others, particle size, density, water content, mineralogy composition, ground temperature, organic matter.
The performance of a VSG system, as horizontal collectors or special forms, is strongly correlated to the kind of sediment at disposal and suddenly decreases in case of dry-unsaturated conditions in the surrounding soil. Therefore, a better knowledge of the relationship between thermal conductivity and water content is required for understanding the VSG systems behavior in saturated and unsaturated conditions.
Key challenge of ITER Project, funded by European Union, is to understand how to enhance the heat transfer of the sediments surrounding the pipes, taking into account the interactions between the soil, the horizontal heat exchangers and the surrounding environment.
In order to obtain reliable data for modelling, an interdisciplinary approach is used. In laboratory the physical-thermal properties of more than 15 soil mixtures, consisting in (i) natural soil, (ii) pure sand and (iii) mixtures of pure sand and clay additives, have been tested under different water content percentages and different consolidation degree. Then the same parameters are monitored in the project case study, in Eltersdorf, (Germany), where five helix collectors are installed in horizontal trenches filled in with five different mixtures already tested in laboratory. In addition, a monitoring system allows to record every 15 minutes, by means of devoted sensors, values related to ground temperature (undisturbed, inside and outside each helix), fluid temperature and flow running in the collectors, volumetric water content at 20 and 60 cm depth. Moreover, a meteorological station provides climatic data acquisition as rainfall, wind speed, relative humidity and air temperature.
The main results achieved until now are useful for future modeling because shed new light (i) on the differences between data collected in laboratory and in the field and (ii) on the influence of the technical solution adopted in situ to fill in the trenches, able to create a non-homogeneous distribution of the soil bodies around the helix.Abstract
5th International Conference Novel Methods for Subsurface Characterization and Monitoring: From Theory to Practice, NovCare 2017, Dresden, Germany, 06-09.06.201
Present and future challenges of urban systems affected by seawater and its intrusion: The case of Venice, Italy
No full textCoastal aquifers and groundwater salinization: an overview of the shallow aquifers in the Venetian coastal plain (NE, Italy)
No full textContaminazione salina nei sistemi acquiferi dell’entroterra meridionale dellalaguna di Venezia
No full textContaminazione salina nei sistemi acquiferi dell'entroterra meridionale della laguna di Venezia
No full textStratigraphy modeling and thermal conductivity computation in areas characterized by Quaternary sediments
No full textA feasibility plan for the exploitation of low enthalpy geothermal resources at regional scale requires a map of the ground thermal conductivity. Available information often comes from heterogeneous well log data related to boreholes drilled for various purposes (e.g. irrigation) and whose spatial distribution is suboptimal. Therefore, a suitable interpolation technique is necessary. An approach based on local evaluation of the mode of distribution of the subsoil geological species is proposed here. It provides a stratigraphy model, the equivalent ground thermal conductivity and the corresponding statistical/geometrical significance in the nodes of a regular grid. Besides a validation with synthetic data of the MATLAB/GNU Octave implementation of the method (GRIDWELL toolbox), the results of its application to the data from Apulia's plain areas are shown here
Detecting the origin of salt water contamination in groundwater in a lagoon area by the combined use of geophysical and geochemical tools: the example of the southern Venice Lagoon mainland
No full textThe south sector of the Venice Lagoon mainland is a territory characterized by the presence of saline contamination.
Sea water contamination is registered in groundwater near the coastline, and tidally dispersed sea water is usually found in the riverbeds, suspended above the surrounding land. Geophysical research, confirmed by some deep drillings, detected throughout the territory the existence of a deep salt-water aquifer storing fossil saline water at a depth of about 450 m. This research aimed to verify whether the deep fossil saline water could contribute to the salt contamination of the lagoonal mainland. Therefore, together with a critical revision of old geophysical data (vertical electric sounding -VES-, acquired during the 1970s), new geophysical sounding and geochemical analysis were performed. The revision of the geophysical data shows the presence of a dislocation of the aquifer basement: a deep buried tectonic lineament seems to affect the salt-groundwater distribution, apart from the lateral and vertical variability of permeability and the textural pattern of the stratigraphic succession. Moreover, the geochemical-isotopic analyses show the presence of fossil water in the unconfined aquifer. Therefore, salt contamination may be due to saline ingression from the sea and the lagoon, and also by the mobilization of fossil brines by means of a combined action of tectonics and fresh water dilution processes. The aim of this study is to understand the real origin of saltwater by means of chemical and isotopic analysis of water samples collected all over the area, determining the groundwater age and chemical composition and therefore, distinguishing old fossil waters from actual marine water
New geophysical knowledge of groundwater systems in Venice estuarine environment
No full textIssues 1-2
Thermo-physical properties of Euganean Hills lithologies (Padua, North-Eastern Italy) related to underground thermal storage feasibility
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