The 5 April 2003 paroxysm at Stromboli: a review of geochemical observations

This paper reviews the published geochemical variations observed during the 2002–2003 eruption at Stromboli volcano. At the end of 2002, a new eruption began at Stromboli with a lava flow that lasted until the end of July 2003. On 5 April 2003 an explosive paroxysm occurred with the ejection of bombs that reached the village of Ginostra, about 4 km from the craters. During the eruption, specific variations in chemical composition of ground waters and summit fumaroles were recorded before the explosion, most of them for the first time. The water pH decreased significantly (0.5 units) and the dissolved CO2 increased in two thermal wells (Cusolito and Zurro) located near Stromboli harbor from March until 5 April. Peaks in the dissolved He were also observed at all the sampling sites. All of these changes in the thermal aquifer suggested a pressurization of the system due to the degassing of a volatile-rich magma at depth. In the summit area the SO2/HCl and SO2/HF ratios in the plume increased suddenly between 1 and 3 April due to the degassing of an S-rich magma that was approaching the shallow levels of the plumbing system, and this was involved in the explosion that occurred a few days later. This eruption was the first at Stromboli to be analyzed using geochemical models. The variations observed in the basal aquifer and in the summit area occurred on very different timescales: a few weeks and few days, respectively

Carbon Dioxide degassing at Latera caldera (Italy): evidence of geothermal reservoir and evaluation of its potential energy

In order to test the potentiality of soil CO2 diffuse degassing measurements for the study of underground mass and heat transfer in geothermal systems detailed surveys were performed at Latera Caldera which is an excellent test site, due to the abundant available subsurface data. Over 2500 measurements of soil CO2 flux revealed that endogenous CO2 at Latera Caldera concentrates on a NE-SW band coinciding with a structural high of fractured Mesozoic limestones hosting a water-dominated high-enthalpy geothermal reservoir. The total hydrothermal CO2 degassing from the structural high has been evaluated at 350 t d-1 from an area of 3.1 km2. It has been estimated that such a CO2 release would imply a geothermal liquid flux of 263 kg s-1, with a heat release of 239 MW. The chemical and isotopic composition of the gas indicates a provenance from the geothermal reservoir and that CO2 is partly originated by thermal metamorphic decarbonation in the hottest deepest parts of the system and partly has a likely mantle origin. The ratios of CO2, H2, CH2 and CO to Ar, were used to estimate the T-P conditions of the reservoir. Results cluster at T ~ 200-300°C and PCO2 ~ 100-200 bars, close to the actual well measurements. Finally the approach proved to be an excellent tool to investigate the presence of an active geothermal reservoir at depth and that the H2-CO2-CH4-CO-Ar gas composition is a useful T-P geochemical indicator for such CO2 rich geothermal systems

Obsidians of Pantelleria (Strait of Sicily): A Petrographic, Geochemical and Magnetic Study of Known and New Geological Sources

This paper provides new petrochemical and paleomagnetic data from obsidian sub-sources on the island of Pantelleria, exploited since the Neolithic. Data has been obtained from 14 obsidian samples from 4 locations: Fossa della Pernice (2 sites), Salto la Vecchia and Balata dei Turchi. Here, we aim to better characterize these obsidians using a cross-disciplinary and multi-analytical approach, to further understand their archaeological significance. Major element analyses (EMP) have enabled two compositional super-groups to be distinguished: (i) Fossa della Pernice, less peralkaline and (ii) Balata dei Turchi-Salto la Vecchia, distinctly more peralkaline and having almost identical chemical patterns. Trace element analyses (LA-ICP-MS) corroborate major element groupings, with the Balata dei Turchi-Salto la Vecchia super-group being further characterized by a pronounced negative europium anomaly. Glass H2O contents (FT-IR) reveal an overlap among all the sub-sources (H2O = 0.1-0.3 wt. %). Magnetic methods have refined the petrochemical groupings, permitting further distinction between Balata dei Turchi-Salto La Vecchia and the Fossa della Pernice super-groups. The occurrence of sub-microscopic (< 1 μm) ferromagnetic minerals results in different magnetic susceptibility and Natural Remanent Magnetization values and allows the best distinction among the products from the chosen sites. When compared with obsidian tools excavated from Bronze-age settlements on the island of Ustica (230 km NE of Pantelleria), 12% are distinctly peralkaline, indicating their provenance to be from the Balata dei Turchi sub-source

Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy)

We report on a continuous-measurement campaign carried out in Vulcano (Aeolian islands, Sicily), devoted to the simultaneous monitoring of CO2 and H2O concentrations. The measurements were performed with an absorption spectrometer based on a semiconductor laser source emitting around a 2-μm wavelength. The emitted radiation was selectively absorbed by two molecular ro-vibrational transitions specific of the investigated species. Data for CO2 and H2O concentrations, and CO2 soil diffusive flux using an accumulation chamber configuration, were collected at several interesting sampling points on the island (Porto Levante beach- PLB, Fossa Grande Crater – FOG- and Valley of Palizzi, PAL). CO2/H2O values, measured on the ground, are very similar (around 0.019 (± 0.006)) and comparable to the previous discrete detected values of 0.213 (Fumarole F5-La Fossa crater rim) and 0.012 (Fumarole VFS – Baia Levante beach) obtaid during the 1977–1993 heating phase of the crater fumaroles

Health Hazard from Gas Emissions in the Quaternary Volcanic Province of Latium (Italy)

The Quaternary Volcanic Province of Central Italy is characterized by zones with a huge endogenous degassing where frequent, sometimes lethal, accidents occur to people and animals. The emitted gas has a deep origin (volcanic or mantle) and is mainly composed by CO2 (up to 98%) and H2S (1-4%), which may reach dangerous concentrations both in open air and indoor. Here we present the results of a multiparametric geochemical study carried out in 2007-2009 in the Provinces of Rome and Viterbo (Latium), with the aim of assessing the health hazard of their main gas emission sites (GES). Three types of GES were investigated: 1. natural, open-air thermal pools, 2. within natural reserves, 3. near to inhabited zones. More than 15 GES have been studied, and here we will illustrate some of the cases with the highest hazard. Results are presented for the sites of Vejano and Mola di Oriolo (Viterbo), Caldara di Manziana, Tor Caldara and Solforata di Pomezia (Rome). Cava dei Selci is a well-known inhabited area of the volcanic complex of Colli Albani (Rome). In each site, multi-technique surveys have been carried out to estimate the total gas output and its concentration in air, by measuring: CO2 and H2S viscous and diffuse flux (the latter by accumulation chamber), CO2 and H2S concentration in air (by TDL profiles and punctual Draeger measurements); moreover, the chemical and isotopic composition of the gas was determined in each site. In all these zones, lethal air concentrations may be reached by both H2S and CO2, but more frequently by the first. Recommendations for risk reduction were given to Civil Protection authorities.Comission of Cities and Volcanoes (CaV) of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) Agencia Española de Cooperación Internacional para el Desarrollo (AECID), Gobierno de España Ministerio de Ciencia e Innovación (MICINN), Gobierno de España Unidad Militar de Emergencias (UME), Ministerio de Defensa, Gobierno de España Agencia Canaria de Investigación, Innovación y Sociedad de la Información (ACIISI), Gobierno de Canarias Viceconsejería de Infraestructuras y Planificación, Gobierno de Canarias Consejería de Turismo, Gobierno de Canarias Consejería de Medio Ambiente y Ordenación Territorial, Gobierno de Canarias Viceconsejería de Cultura y Deportes, Gobierno de Canarias Instituto Español de Oceanografía (IEO)Instituto Geológico y Minero de España (IGME)Instituto Geográfico Nacional (IGN)Academia Canaria de Seguridad Federación Canaria de Municipios (FECAM) Universidad de La Laguna (ULL)Instituto de Estudios Hispánicos de Canarias (IEHC) CajaCanariasPublishedPuerto de la Cruz, Tenerife, Spain1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive4.5. Studi sul degassamento naturale e sui gas petroliferiope

Level of carbon dioxide diffuse degassing from the ground of Vesuvio: comparison between extensive surveys and inferences on the gas source

An extensive campaign of diffuse CO2 soil flux was carried out at the cone of Vesuvio in October 2006 with two main objectives: 1) to provide an estimation of CO2 diffusely discharged through the soils in the summit area and 2) to evidence those sectors of the volcano where structural and morphological conditions could favour the gas output. The survey consisted of 502 measurements of soil CO2 flux homogenously distributed over an area of about 1.8 km2. Results of this survey were compared with those obtained during a similar campaign carried out by Frondini et al. in 2000, from which we have taken and reinterpreted a subset of data belonging to the common investigated area. Graphical statistical analysis showed three overlapping populations in both surveys, evidencing the contribution of three different sources feeding the soil CO2 degassing process. The overall CO2 emission pattern of 2006 is coherent with that observed in 2000 and suggests that a value between 120 and 140 t/day of CO2 is representative of the total CO2 discharged by diffuse degassing from the summit area of Vesuvio. The preferential exhaling area lies in the inner crater, whose contribution resulted in 45.3% of the total CO2 emission in 2006 (with 62.8 t/day) and in 57.4% (with 70.3 t/day) in 2000, although its extension is only 13% of the investigated area. This highly emissive area correlated closely with the structural discontinuities of Vesuvio cone, mainly suggesting that the NW-SE trending tectonic line is actually an active fault leaking deep gas to the bottom of the crater. The drainage action of the fault could be enhanced by the “aspiration” effect of the volcanic conduit

Environmental pre-exploitation monitoring of Torre Alfina geothermal system (Central Italy)

An interesting project of geothermal pilot plant, with no-gas emission in atmosphere, has been submitted for approval in the medium-enthalpy geothermal field of Torre Alfina. This prompted us to develop a geochemical and geophysical monitoring of the area with the aim of establishing a background information to reco-gnize anomalous gas emission, induced seismicity and subsidence, possibly related to the field exploitation. The exploration conducted by Enel in the years ‘70 - '80, including the drilling of 9 deep wells, has shown the existence of a medium-enthalpy geothermal field in the Torre Alfina zone, in central Italy. The area has been affected by a very complex geological evolution during the Neogene. It was affected by the Quaternary volcanism of the Tyrrhenian margin which, reached its climax between 0.6 and 0.3 Ma. The present stress field around Quaternary volcanoes of central Italy has a NE to ENE direction of extension, in agreement with the alignment of Quaternary volcanoes and earthquake fault plane solutions, with T axes preferentially oriented between NE and ENE.PublishedPrague, Czech Republic, June 22 to July 2, 20156T. Sismicità indotta e caratterizzazione sismica dei sistemi naturaliope

Hazardous gas emissions from the flanks of the quiescent Colli Albani volcano (Rome, Italy)

Gas hazard was evaluated in the three most important cold gas emission zones on the flanks of the quiescent Colli Albani volcano. These zones are located above structural highs of the buried carbonate basement which represents the main regional aquifer and the main reservoir for gas rising from depth. All extensional faults affecting the limestone reservoir represent leaking pathways along which gas rises to the surface and locally accumulates in shallow permeable horizons forming pressurized pockets that may produce gas blowout when reached by wells. The gas, mainly composed by CO2 (>90 vol.%), contains appreciable quantities of H2S (0.35-6 vol.%), and both represent a potentially high local hazard. Both gases are denser than air and accumulate near ground where they may reach hazardous concentrations, and actually lethal accidents frequently occur to animals watering at local ponds. In order to evaluate the rate of degassing and the related hazard, CO2 and H2S diffuse soil flux surveys have been repeatedly carried out by accumulation chamber. The viscous gas flux of some important discrete emissions has been also evaluated and the CO2 and H2S air concentration measured by portable devises and by Tunable Diode Laser profiles. The minimum potential lethal concentration of the two gases (250 ppm for H2S and 8 vol.% for CO2) is 320 times higher for CO2, whereas the CO2/H2S concentration ratio in the emitted natural gas is significantly lower (15-159). This explains why H2S reaches hazardous, even lethal, concentrations more frequently than CO2. A relevant hazard exists for both gases in the depressed zones (channels, excavations) particularly in the non-windy early hours of the day

Environmental pre-exploitation monitoring of Torre Alfina geothermal system (Central Italy)

An interesting project of geothermal pilot plant, with no-gas emission in atmosphere, has been submitted for approval in the medium-enthalpy geothermal field of Torre Alfina. This prompted us to develop a geochemical and geophysical monitoring of the area with the aim of establishing a background information to reco-gnize anomalous gas emission, induced seismicity and subsidence, possibly related to the field exploitation. The exploration conducted by Enel in the years ‘70 - '80, including the drilling of 9 deep wells, has shown the existence of a medium-enthalpy geothermal field in the Torre Alfina zone, in central Italy. The area has been affected by a very complex geological evolution during the Neogene. It was affected by the Quaternary volcanism of the Tyrrhenian margin which, reached its climax between 0.6 and 0.3 Ma. The present stress field around Quaternary volcanoes of central Italy has a NE to ENE direction of extension, in agreement with the alignment of Quaternary volcanoes and earthquake fault plane solutions, with T axes preferentially oriented between NE and ENE

Importance of meteorological variables for aeroplankton dispersal in an urban environment

Passive wind dispersal is one of the major mechanisms through which organisms disperse and colonize new areas. The detailed comprehension of which factors affect this process may help to preserve its efficiency for years to come. This is especially important in the current context of climate change, which may seriously alter weather regimes that drive dispersal, and is crucial in urban contexts, where biodiversity is dramatically threatened by pollution and fragmentation of natural patches. Despite its interest, the analysis of factors affecting aeroplankton dispersal in urban environments is rare in literature. We sampled aeroplankton community uninterruptedly every 4 hours from 17th May to 19th September 2011 in the urban garden of Parco d'Orléans, within the campus of the University of Palermo (Sicily). Sampling was performed using a Johnson-Taylor suction trap with automatized sample storing. Weather variables were recorded at a local meteorological station. Overall, 11,739 insects were caught during the present study, about 60% of these belonged to the order Hymenoptera, with particular presence of families Agaonidae and Formicidae. The suction trap also captured specimens of very small size, and in some cases, species caught were new records for Italy. Composition and abundance of aeroplankton community was influenced by alternation day/night, as well as by daily fluctuations of climatic variables, for example fluctuating temperature . The diversity of samples was also studied and resulted higher when wind blew from the nearby green area. Our findings confirm that passive transport of arthropods strictly depends on weather conditions, and that the presence of natural areas within the urban environment significantly contribute to raise aeroplankton diversity, eventually fuelling overall biodiversity at a local scale. We discuss how climate change may affect future dispersal of these organisms