The alluvial aquifer of the Oltrepò Pavese plain sector (Po Valley, Northern Italy) is naturally contaminated by Na–Cl paleo-waters, rising from the tertiary marine substratum and mixing with the shallow groundwater. This phenomenon is localised along a buried tectonic discontinuity known as Vogherese Fault. A hydro-chemical (sampling for chemical analysis, log of electrical conductivity and temperature, continuous monitoring system) and a geophysical (VLF-EM, 2D and 3D ERT surveys, resistivity profiling, resistivity depth soundings) study was carried out to investigate the phenomenon. The research highlighted a spot spatial distribution of the saline contamination, suggesting the existence of isolated plumes of saltwater within the aquifer and a temporal variability of groundwater’s salinity. These results allowed at formulating a conceptual model based on the regional hydraulic continuity between the fracture network of the aquifer in the Apennines mountain range and the porous aquifer in the Oltrepò Pavese plain. Severe recharge events in the Apennines could be able to activate a mass or pressure transfer from the fractured to the porous aquifer and to cause the uprising of deep paleo-waters into the alluvial aquifer.
The Uprising of Deep Saline Paleo-Waters into the Oltrepò Pavese Aquifer (Northern Italy): Application of Hydro-Chemical and Shallow Geophysical Surveys
PILLA, GIORGIO;TORRESE, PATRIZIO;
2015-01-01
Abstract
The alluvial aquifer of the Oltrepò Pavese plain sector (Po Valley, Northern Italy) is naturally contaminated by Na–Cl paleo-waters, rising from the tertiary marine substratum and mixing with the shallow groundwater. This phenomenon is localised along a buried tectonic discontinuity known as Vogherese Fault. A hydro-chemical (sampling for chemical analysis, log of electrical conductivity and temperature, continuous monitoring system) and a geophysical (VLF-EM, 2D and 3D ERT surveys, resistivity profiling, resistivity depth soundings) study was carried out to investigate the phenomenon. The research highlighted a spot spatial distribution of the saline contamination, suggesting the existence of isolated plumes of saltwater within the aquifer and a temporal variability of groundwater’s salinity. These results allowed at formulating a conceptual model based on the regional hydraulic continuity between the fracture network of the aquifer in the Apennines mountain range and the porous aquifer in the Oltrepò Pavese plain. Severe recharge events in the Apennines could be able to activate a mass or pressure transfer from the fractured to the porous aquifer and to cause the uprising of deep paleo-waters into the alluvial aquifer.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
