Giuliano Gabbani

Metallogeny, exploitation and environmental impact of the Mt. Amiata mercury ore district (Southern Tuscany, Italy)

The Mt. Amiata mining district (Southern Tuscany, Italy) is a world class Hg district, with a cumulate production of more than 100,000 tonnes of Hg, mostly occurring between 1870 and 1980. The Hg mineralization at Mt. Amiata is younger than 0.3 Ma, and is directly related to shallow hydrothermal systems similar to presentday geothermal fields of the region. There is likely a continuum of Hg deposition to present day, because Hg emission from geothermal power plants is on-going. In this sense, the Mt. Amiata deposits present some analogies with hot-spring type deposits of western USA, although an ore deposit model for the district has not been established. Specifically, the source of Hg remains highly speculative. The mineralizing hydrothermal fluids are of low temperature, and of essentially meteoric origin. Recent results by our research group indicate that, 30 years after mine closure, the environmental effects of Hg contamination related to mining are still recorded by the ecosystem, namely on waterways of the Paglia and Tiber River basins. In particular, the close spatial connection between the town of Abbadia San Salvatore, the Hg mine within its immediate neighborhood, and the drainage catchment of the Paglia River has an influence also on Hg speciation, transported mainly in the particulate form by the river system. The extent of Hg contamination has been identified at least 100 km from Abbadia San Salvatore along the Paglia-Tiber River system. Estimated annual Hg mass loads transported by the Paglia River to the Tiber River were about 11 kg yr-1. However, there is evidence that flood events may enhance Hg mobilization in the Paglia River basin, increasing Hg concentrations in stream sediment. The high methyl-Hg/Hg ratio in water in this area is an additional factor of great concern due to the potential harmful effects on human and wildlife health. Results of our studies indicate that the Mt. Amiata region is at present a source of Hg of remarkable environmental concern at the local, regional (Tiber River), and Mediterranean scales. Ongoing studies are aimed to a more detailed quantification of the Hg mass load input to the Mediterranean Sea, and to unravel the processes concerning Hg transport and fluid dynamics.

Geomechanical Characterization and Stability Analysis of the Bedrock Underlying the Costa Concordia Cruise Ship

The shipwreck of the Costa Concordia cruise ship, which ran aground on 13 January 2012 on the northwestern coast of Giglio Island (Italy), required continuous monitoring of the position and movement of the vessel to guarantee the security of workers and rescuers operating around and within the wreck and to support shipwreck removal operations. Furthermore, understanding the geomechanical properties and stability behaviour of the coastal rock mass and rocky seabed underlying the ship was of similar importance. To assess the stability conditions of the ship, a ground-based monitoring system was installed in front of the wreck. The network included a terrestrial laser scanner (TLS) device, which was used to perform remote semiautomatic geomechanical characterization of the observed rock mass. Using TLS survey techniques, three main discontinuity sets were identified in the granitic rock mass of Giglio Island. Furthermore, a multibeam bathymetric survey was used to qualitatively characterize the seabed. To integrate the processed TLS data and quantitatively describe the rock mass quality, a subsequent field survey was carried out to provide a rock mass geomechanical evaluation (from very good to moderate quality). Based on the acquired information, kinematic and stability analyses were performed to create a spatial prediction of rock failure mechanisms in the study area. The obtained kinematic hazard index values were generally low; only the plane failure index reached slightly higher values. The general stability of the rock mass was confirmed by the stability analysis, which yielded a high safety factor value (approximately 12).

Le potenzialità geotermiche di alcune aree del Medio Campidano oggetto di ricerca di risorse a media entalpia

The middle part of the Campidano Valley has gained a renewed interest in the geothermal exploration due to the attention of private investors determined to define the presence of medium-enthalpy geothermal resources in the subsurface of this sector of Sardinia. The study area is a portion of the Plio-Pleistocene Campidano Graben that is bordered both to the north and to the south by structural highs (e.g. the Iglesiente-Sulcis horst) mostly made of Paleozoic metamorphic rocks, deformed and recrystallized during the Variscan Orogeny. Available data suggest that the geothermal reservoir can be positioned in the fractured Paleozoic metamorphic rocks below the Miocene-Quaternary sedimentary filling of the Campidano Graben. The thermal fluids locally reach the surface in correspondence of the border normal fault systems of the graben.Research activities include a first phase of surface investigations, such as geological, hydrogeological and geochemical surveys, and fa geophysical prospecting aimed to assess the quality and quantity of the geothermal resources.

La tecnologia innovativa, senza dragaggi convenzionali, per la rimozione degli inquinanti dai sedimenti e il riutilizzo selettivo degli stessi dopo separazione granulometrica: Un caso in Sardegna

An innovative technology of sludging and separation of pollutants from sediments of varying grain size has been carried out in a basin in SW Sardinia. The removal of sediment and materials accumulated in ports, docks and all areas, where the morphology favours these natural phenomena, is often a problematic operation mostly due to the environmental impact. Sludging is commonly performed mechanically with conventional dredging. This work deals with the problematics and types of intervention of sludging and, in addition to the different regulations concerning this topic, offers a patented innovative solution. The sediments are removed doing a grain-size selection of the particles, and, most important, the polluted material and harmful substances are taken away without contaminating the surrounding environment. This technology, now mature and well experienced, is also supportive to the nourishment of the coasts with a well-defined grain size material. This is a valuable response to the problems, often present in the existing nourishments, related to the natural remobilization of the new sandy material during the first sea storm which tends to bring the seabed back to the natural conditions prior to sludging.