CHARACTERIZATION OF BAGNI DI LUSNIZZA (UDINE) SULPHUREOUS WATER RESOURCES BY INTEGRATED GEOPHYSICAL METHODS

The aim of this study is to characterize the sulphureous water resource feeding the Bagni di Lusnizza historical spring (located in the ‘Rio dello Solfo’ Valley, north-eastern Alps), through an integrated geological, geochemical and geophysical study. The reconstruction of the hydrogeologic framework in this complex mountain area, including the circulation pathways in the upper 100 m and the mixing zones between deep sulphureous and shallow meteoric waters, substantially benefits from the Electric Resistivity Tomography (ERT) and from the electromagnetic measurements (FDEM and VLF). They allow to image the buried geological structures (such as the morphology and fracturing of the bedrock), to identify the mineralized water saturation zones in the debris deposits (resistivity values lower than 100 Ohm m) and to speculate on the potential fracture zones through which the sulphureous water rise, providing a preliminary conceptual model for the hydrogeologic recharge. The shallow geophysical survey was first acquired to characterize the upper 10 m of debris deposits and outcropping rocks and to calibrate the indirect geophysical data with the geochemical measurements and geological information. The deep imaging was carried out to characterize the entire filling of the valley and possibly the buried bedrock. The successful results of the geophysical measurements provide the background model for a more focused survey in order to locate one or two wells intercepting the rising sulphureous waters (before they mix with the shallow freshwater), with the aim to exploit temperature and geochemical properties of the deep resource.