Description: Vengono mostrati i primi risultati dei rilievi geofisici e geochimici nella zona di Guidonia che hanno consentito una caratterizzazione geologica e strutturale preliminare fornendo elementi utili per la comprensione della genesi del fenomeno di sprofondamento in atto e della sua evoluzione.

Description: Published

Description: 8 maggio 2014, Roma

Description: 7A. Geofisica per il monitoraggio ambientale

Description: 6SR VULCANI – Servizi e ricerca per la società

Description: A GIS-based procedure for mapping pluvial flood risk in urban areas is proposed; risk is expressed through an index calculated as the sum of susceptibility and potential impact, combined in a matrix. The susceptibility is defined as the probability of a flooding to occur, because of the ground morphology and the spatial probability density of historical floodings. The potential impact was evaluated by considering the consequences of damages on human health, environment, cultural heritages and economic activities, and accounts for the potential cost of damage. Both the susceptibility and the potential impact are calculated by elaborations of base-data in GIS environment. Despite many limitations, the methodology furnishes a tool for a preliminary screening of areas potentially subjected to pluvial flood, useful for a municipal scale mapping. It permits comparative analysis for detecting areas higher at risk, helping prioritizing the emergency management and the planning of mitigation actions.

Description: Published

Description: 64-84

Description: 7A. Geofisica per il monitoraggio ambientale

Description: JCR Journal

Description: Geological gas seepage in petroleum-bearing sedimentary basins is an important natural source of atmospheric methane. In methane budget models geological emissions are generally considered constant over time, not affecting decadal atmospheric methane changes. Here, we report the case of a considerable sub-decadal variation of methane seepage from one of the largest thermogenic gas seep sites in Europe, Katakolo Harbour (Western Peloponnese, Greece). Based on gas flux measurements by accumulation chamber performed in 2010 and 2018, methane emission from cracks and fissures throughout the asphalt and concrete pavement of the harbour increased about four times (from 57 to 225 kg d􀀀 1) with emission factor changing from ~4,000 to 15,000 t km􀀀 2 y􀀀 1. Multiple lines of evidence, including mechanical deformation and fissuring of concrete and asphalt pavement, increased exhalation with constant fissure conditions, and no significant cracking with operating corrosion from 2004 to 2010, suggest that the methane emission increase is mainly due to intensification of subsurface gas flow (seepage) after 2010. Deep gas pressure and fault permeability variations, likely induced by the numerous earthquakes of the region, might have played a role. We estimate that if similar short-term variations of emission factor occur in large seepage areas worldwide, the global geological methane emission can significantly change, contributing to decadal changes of atmospheric methane budget.

Description: Published

Description: 104578

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: The map shows the result of a procedure for pluvial flood hazard (PFH) mapping in urban areas, developed by using easy to find data, usually available from local authorities. Data were processed using a sequence of tools in a GIS environment. Two parameters have been evaluated: (1) susceptibility, defined as the probability of a flood occurring in a certain area (‘flood-prone areas’) which depends on the ground morphology (i.e. presence of depressions, fill volume of depressions) and spatial density of previously observed floods and (2) potential impact, formed from all factors influencing the damage (e.g. value of exposed heritage or number of people potentially involved), as well as the induced hazard due to damage. Susceptibility and potential impact were each divided into five classes and a score matrix was constructed; the final PFH is then defined by the summation of the scores within the matrix. The methodology used is suitable for a comprehensive, mostly automatic, first-level analysis of PFH in urban areas, and it is easily replicable. The obtained flood hazard map could provide a useful tool for civil protection purposes, that is, for hazard evaluation and emergency planning.

Description: Published

Description: 545 – 553

Description: 7A. Geofisica per il monitoraggio ambientale e geologia medica

Description: JCR Journal

Description: Continuous monitoring has been carried out at a fluvial flood-plain site near Rome for over a year. There is a mix of biogenic CO2 and deep geogenic CO2 at the site at relatively low concentrations and fluxes compared with other natural CO2 seepage sites studied previously. Factors such as temperature and soil moisture clearly affect the CO2 concentration and flux and seasonal and diurnal influences are apparent. Statistical approaches are being used to try to define these relationships and separate out the two gas components, which would be necessary in any quantification of leakage from CO2 storage.

Description: Published

Description: 3824 – 3831

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: The actively extending axial zone of the southern Apennine mountain belt of Italy is characterized by a substantial flow of nonvolcanic gas to the surface. In this study, we have analyzed the correlation between the active tectonic framework of the Matese Ridge area and the high gas emissions found to the southwest, which includes large amounts of CO2 (up to 99 vol%), CH4 (up to 0.55 vol%), and He (up to 52 ppmv). We measured CO2 and CH4 fluxes of up to 34000 g d–1 and 2000 g d–1, respectively, from zones of focused degassing (gas vents and associated strong diffuse emission). This anomalously high flux of CO2 (advective plus diffusive) indicates that the study area has one of the largest nonvolcanic natural emissions of CO2 ever measured on Earth. The isotope composition of C in CO2 and CH4 shows there is a dominant crustal contribution of emissions (as opposed to a source from the mantle), indicating that thermometamorphism of the buried Apulian Platform carbonates is probably the main cause of CO2 production. This process has likely been enhanced by Quaternary magmatism, which provides an additional local source of heat triggering decarbonation of Apulian Platform limestones and dolostones at depth. The advective flux is concentrated at gas vents located along active fault segments located at the western tip of a major crustal structure, the South Matese fault zone. We believe that the very high gas emission in the Matese Ridge area is the result of both the presence of a dense network of active fault strands, which provides efficient pathways for fluid flow toward the surface, and the dramatically reduced thickness of the clay-rich mélange zone acting elsewhere in the southern Apennines as a top seal overlying the buried Apulian Platform carbonates.

Description: Published

Description: 1697–1722

Description: 7T. Variazioni delle caratteristiche crostali e precursori sismici

Description: JCR Journal

Description: Sediment-Hosted Geothermal Systems (SHGSs) are hybrid geological systems, where volcanic and sedimentary domains interact, leading to mixtures of inorganic and organic gases. Typically characterized by geothermal (thermometamorphic or mantle-derived) CO2 and biotic (microbial or thermogenic) CH4, SHGSs occur in sedimentary basins crossed by magmatic intrusions or involved in volcanic plumbing systems. These systems can be of considerable interest for petroleum exploration and natural greenhouse-gas emission studies, but systematic studies for their characterization and worldwide distribution are missing. Here, we provide a review of SHGSs identified so far, and propose methodological criteria for their definition and identification, based on integrated geological and gas-geochemical parameters. We find that SHGSs are typically characterized by: (a) fluids dominated by mantle or decarbonation-methamorphic CO2 (〉 50 vol%); (b) considerable amounts of CH4 and heavier hydrocarbons (at least 1.5 vol%, generally up to 30–40 vol%), produced by microbial or thermogenic degradation of organic matter hosted in sedimentary rocks; (c) tectonically active sedimentary basins (back-arc, rift zones and foredeep), generally hosting petroleum fields and within ~300 km from recent or ancient volcanic centers. This analysis resulted in a global map including a first set of 33 SHGSs located in North America, Central and Eastern Europe, Far East, Eastern Oceania and Northern New Zealand, and a second set of potential SHGS prone areas, occurring also in South America, North Africa, Middle East and Kamchatka. The present SHGS map can evolve on the basis of more detailed geological analysis and new gas-geochemical data.

Description: Published

Description: 529-544

Description: 1TR. Georisorse

Description: JCR Journal

Description: Radon isotopes (222Rn, 220Rn) are noble, naturally occurring radioactive gases. They originate from the alpha decay of radium isotopes (226Ra, 224Ra), which occur in most materials in the environment, i.e. soil, rocks, raw and building materials. Radon is also found in ground and tap water. The two radon isotopes are chemically identical, but they have very different halflives: 3.82 days for radon (222Rn) and 56 seconds for thoron (220Rn). Thus, they behave very differently in the environment. Both isotopes are alpha-emitters; their decay products are polonium, bismuth and lead isotopes. The main source of radon in air (indoor or outdoor) is soil, where radon concentrations are very high and reach tens of Bq/m3. Radon release from soil into the atmosphere depends on radium (226Ra) concentration in soil, soil parameters (porosity, density, humidity) and weather conditions (e.g. air temperature and pressure, wind, precipitation). Outdoor radon concentrations are relatively low and change daily and seasonally. These changes may be used to study the movement of air masses and other climatic conditions. Radon gas enters buildings (homes, workplaces) through cracks, crevices and leaks that occur in foundations and connections between different materials in the building. This is due to temperature and pressure differences between indoors and outdoors. Indoor radon is the most important source of radiation exposure to the public, especially on ground floor. Radon and its decay products represent the main contributor to the effective dose of ionising radiation that people receive. Radon is generally considered as the second cause of increased risk of lung cancer (after smoking). The only way to assess indoor radon concentration is to make measurements. Different methods exist, but the most common one is to use track-etched detectors. Such detectors may be used to perform longterm (e.g. annual) measurements in buildings. The exposure time is important because indoor radon levels change daily and seasonally. Moreover, radon concentration shows a high spatial variation on a local scale, and is strongly connected with geological structure, building characteristics and ventilation habits of occupants. A European map of indoor radon concentration has been prepared and is displayed. It is derived from survey data received from 35 countries participating on a voluntary basis.

Description: Published

Description: 108-137

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: The monitoring of the integrity of onshore geological carbon capture and storage projects will require an approach that integrates various methods with different spatial and temporal resolutions. One method proven to be quite effective for site assessment, leakage monitoring, and leakage verification is near-surface gas geochemistry, which includes soil gas concentration and gas flux measurements. Anomalous concentrations or fluxes, relative to the natural background values, can indicate the potential occurrence of a leak. However, the natural background can be quite variable, especially for CO2, due to biological production and accumulation in the soil that changes as a function of soil type, land use, geology, temperature, water content, and various other parameters. To better understand how these parameters influence natural, near-surface background values, and to examine the potential of different sampling strategies as a function of the survey goals, this paper reports results from two highly different case studies, one from northern Europe (Volund, Denmark) and one from southern Europe (Sulcis, Sardinia, Italy). The small Voulund site, with its homogeneous soil, climate, and topography, was surveyed twice (in fall and in spring) within the EU-funded SiteChar project to examine the effects of different land-use practices and seasons on baseline values. Forested land was found to have lower CO2 concentrations during both campaigns compared to cultivated and heathland, and higher CH4 values during the spring sampling campaign. Continuous monitoring probes showed much more detail, highlighting seasonal changes in soil gas CO2 concentrations linked primarily to temperature variations. The much larger Sulcis site, studied within an ENEA-funded project on potential CO2-ECBM (Enhanced Coal Bed Methane) deployment, was surveyed at the regional scale and on detailed grids and transects for site assessment purposes. Despite the completely different soil and climate conditions, the statistical distribution of the Sulcis data was similar to that of Volund. Much higher soil gas CO2 anomalies were found at this site, however, due to the less permeable sediments (i.e., better water retention and greater gas accumulation) and the warmer temperatures. Detailed surveys at this site highlighted various significant anomalies, some of which can be explained by near-surface biological processes, whereas others, especially helium anomalies, were more difficult to explain. These results show the utility of baseline surveys and highlight the need for follow-up studies to clarify any unexplained anomalies before any CO2 storage.

Description: Published

Description: 615-633

Description: 1TR. Georisorse

Description: JCR Journal

Description: A multidisciplinary study based mainly on aerophotogeological interpretation and geochemical prospectings were performed in the Comino valley area which extends between Vicalvi and San Donato Val di Comino villages. The studied area covers 70 km2 of a considered key-area in the geological-seismic framework of the Central Apennines. The Comino valley is located in the SW sector of the Central Apennine (Southern Latium) where the “Val Roveto-Atina-Caserta” regional fault has been studied since many years. Indeed, according with some authors, this fault can be interpreted as a crustal discontinuity probably corresponding to a deep step of the Moho. The studied area is also characterized by the presence of secondary tectonic lineaments (e.g. San Donato-Val Comino fault) having a typical Apenninic orientation (NW-SE). The Comino valley is affected by high seismic activity: last destructive earthquake was in May 7, 1984 (ML 5.9) while during 2009 many seismic events (ML 〈 4) have occurred for several months suggesting a new micro-seismic activity. The spatial soil-gas distributions have been compared with the location and orientation of brittle deformations described in the literature and/or recognized by new field surveys, as well as with morphotectonic features obtained by photogeological analysis. Soil gas results show a pervasive character of the radon, helium and methane values. Soil gas prospecting together with geological survey has provided an inedited and detailed mapping of the structural setting of the studied area and in particular new data about the Comino valley have been acquired. The identified structural lineaments by geological survey as well as the He, CH4 and Rn anomalies in soil gas in correspondence of lineament crossing, suggest that such faults may be considered as the surface expression of a deep structure network (probably down to the Moho) playing a role of important avenue for a vertical and rapid migration of endogenetic gases. In particular, the high Rn median value (51.80 Bq/L) in an area without shallow possible radon sources, suggests a deep origin for this gas and therefore a vertical migration through fractured media, i.e. faults and fractures. The elongated gas anomalies show that the area is characterized by tectonic discontinuities oriented mainly NNW-SSE in accordance with and linked to the regional Val Roveto-Atina-Caserta fault and WSW-ENE that suggest transversal fractured zones. The investigated area is also interested by mineralized springs with a high gaseous component: CO2 is the dominant gas (concentrations 〉 95 %, v/v) but also discrete amounts of CH4 have been measured (max value: 4200 ppm). The spatial distribution of thermal springs, cold CO2-rich springs and localized gas emissions suggests that the structural framework of the studied area, i.e. the bordering faults of buried structural highs of the carbonate basement, exerts a strong control on the uprising patterns of fluids.

Description: Unpublished

Description: Torino (Italy)

Description: 3.2. Tettonica attiva

Description: open