The 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.

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

DI SIPIO E.;GALGARO, ANTONIO;
2005

Abstract

The 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.
2005
Groundwater and saline intrusion. Selected papers from the 18th Salt Water Intrusion Meeting
9788478405886
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/1423336
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