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The use of non-invasive field techniques in the study of small topographically closed lakes: two case studies in Sicily (Italy)

Mon, 22 Apr 2013 22:00:00 GMT

Title: The use of non-invasive field techniques in the study of small topographically closed lakes: two case studies in Sicily (Italy) Authors: Madonia, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Cangemi, M.; Göttingen Zentrum Geowissenschaften, Abteilung Geobiologie, Universität Göttingen, Germany; Di Trapani, F. P.; Legambiente, Comitato regionale siciliano, Palermo, Italy Abstract: Small endhoreic (topografically closed) lakes represent a little percentage of continental waters but, in arid or sub-arid regions, they develop special ecosystems potentially prone to ecological involution due to climatic changes. The mandatory use of light, non-invasive field techniques is often required, especially in protected areas. In the present work the use of non-invasive techniques like GPS−based bathymetric and photographic surveys have been applied to the study of two lakes, Specchio di Venere and Sfondato (Sicily, southern Italy), both natural reserves. The comparison between historical surveys and modern GPS−based bathymetries highlighted the difficulty of using the former for the reconstruction of climatic-induced variations due to the low number of measurements (spatial aliasing). In particular, at the intracaldera Lake Specchio di Venere, a high resolution survey gave new insights into a peculiar geo-ecosystem whose evolution is driven by both volcanic phenomena and biomineralization processes. On the contrary, the morphology of Lake Sfondato floor is much more simple and driven only by the superimposition of a detrital sedimentation on the initial collapse that generated the lake. The comparison betweem direct measurements and estimated changes of lake level, carried out between February 2008 and October 2009 variations, allowed us to test different hypotheses of hydrological balances, leading to opposite conclusions with respect to previous studies and remarking the fundamental importance of direct measurements in the validation of theoretical hydrological models.

Influence of volcanic activity on the quality of water collected in roof water catchment systems at Stromboli Island (Italy)

Mon, 31 Dec 2012 23:00:00 GMT

Title: Influence of volcanic activity on the quality of water collected in roof water catchment systems at Stromboli Island (Italy) Authors: Madonia, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Cangemi, M.; Dip. DiSTeM, Università di Palermo; Bellomo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia Abstract: With the aim of detailing the interaction between volcanic emissions and water harvesting by Roof Water Catchment Systems (RWCSs), the present work illustrates the results of a study carried out at Stromboli Island, a small but densely populated active volcanic area in the South of Italy. Concentrations of major and trace elements determined in RWCS waters and sediments revealed clear clues of a contamination with gases and suspended particles of volcanic origin, even if the values of those contaminants considered by the World Health Organization as dangerous for human health are always belowtheMaximumAdmitted Concentration (MAC). In particular, cistern water showed a composition similar to local coastal rainwater, with dissolved ions related not only to sea aerosol but also to volcanic gases and ash leaching,with a secondary enrichment in Ca ions due to the interactionwith the limewashed surfaces of both roofs and cisternwalls. The simulation of the potential increase in dissolved chemical species due to volcanic ash deposition on the water catchment surfaces indicates the possible exceedance of the MAC for several species. The symptoms of fluorosis affecting elderly people who were young at the time of the 1930–40 volcanic crisis is a clue of a possible volcanogenic fluorine contamination. On the other way, the simulation of the digestion process on solid volcanogenic particulate ingested with drinkingwater highlighted a potential dramatic increase (orders of magnitudes) of dangerous element concentrations in stomach fluids above theirMACs. Despite the evidence of potential health risks induced by volcanic activity, no anamnesic evidence of related pathologies has been found among Stromboli population. This apparent discrepancy is solved taking into account the positive feedback among the good practice in maintaining clean conditions in the harvested waters and the prevalent fallout of volcanogenic ashes away from the main inhabited areas, favoured by the morphological setting of the island and its wind regime.

New insights from seismic tomography on the complex geodynamic evolution of two adjacent domains: Gulf of Cadiz and Alboran Sea

Mon, 31 Dec 2012 23:00:00 GMT

Title: New insights from seismic tomography on the complex geodynamic evolution of two adjacent domains: Gulf of Cadiz and Alboran Sea Authors: Monna, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cimini, G. B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Montuori, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Matias, L.; Centro de Geofísica, Universidade de Lisboa, Lisbon, Portugal.; Geissler, W. H.; Alfred-Wegener-Institut für Polar- und Meeresforschung, Bremerhaven, Germany.; Favali, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: In this study, we present a three-dimensional P wave upper-mantle tomography model of the southwest Iberian margin and Alboran Sea based on teleseismic arrival times recorded by Iberian and Moroccan land stations and by a seafloor network deployed for 1 year in the Gulf of Cadiz area during the European Commission Integrated observations from NEAR shore sourcES of Tsunamis: towards an early warning system (EC NEAREST) project. The three-dimensional model was computed down to 600 kmdepth. The tomographic images exhibit significant velocity contrasts, as large as 3%, confirming the complex evolution of this plate boundary region. Prominent high-velocity anomalies are found beneath Betics-Alboran Sea, off-shore southwest Portugal, and north Portugal, at sublithospheric depths. The transition zones between high- and low-velocity anomalies in southwest and south Iberia are associated to the contact of oceanic and continental lithosphere. The fast structure below the Alboran Sea-Granada area depicts an L-shaped body steeply dipping from the uppermost mantle to the transition zone where it becomes less curved. This anomaly is consistent with the results of previous tomographic investigations and recent geophysical data such as stress distribution, GPS measurements of plate motion, and anisotropy patterns. In the Atlantic domain, under the Horseshoe Abyssal Plain, the main feature is a high-velocity zone found at uppermost mantle depths. This feature appears laterally separated from the positive anomaly recovered in the Alboran domain by the interposition of low-velocity zones which characterize the lithosphere beneath the southwest Iberian peninsula margin, suggesting that there is no continuity between the high-velocity anomalies of the two domains west and east of the Gibraltar Strait.

Geochemistry of free and dissolved gases in the Amik basin area (Turkey) and its relationships with the tectonic setting

Sun, 07 Apr 2013 22:00:00 GMT

Title: Geochemistry of free and dissolved gases in the Amik basin area (Turkey) and its relationships with the tectonic setting Authors: Galip, Y.; Eskisehir Osmangazi Üniversity, Turkey; Italiano, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Yang, T.F.; National Taiwan University, Taiwan; Yalcin, T.H.; Istanbul Technical University, Turkey; Rojay, B.; Middle East Technical University, Ankara, Turkey; Gulbey, A.H.; Eskisehir Osmangazi Üniversity, Turkey; Yasin, D.U.; skisehir Osmangazi Üniversity, Turkey; Ozacar, A.; Middle East Technical University, Ankara, Turkey; D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Bellomo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Fu, C.-C.; National Taiwan University, Taiwan; Lai, C.-W.; National Taiwan University, Taiwan Abstract: Twenty-two gas samples were collected in August 2012 in the area of Amik basin (Turkey). Two samples were collected from gas seeps, one was a bubbling gas in a thermal spring, while the remaining were dissolved gases from cold and thermal groundwaters (T 16-43 °C). All gases were analysed for their chemical composition (He, H2, O2, N2, CH4 and CO2) and for their He isotopic composition. Dissolved gases were also analysed for the carbon isotopic composition of the total dissolved carbon (TDC), while free gases also for their higher hydrocarbon (C1 – C5) content and for D of H2 and CH4, 13C of CH4 Basing on their chemical composition, the gases can be roughly subdivided in three groups. Most of the dissolved gases (16) belonging to the first group were collected from springs or shallow wells (< 150 m depth). All these samples contain mainly atmospheric gasses with very limited H2 (< 80 ppm) and CH4 (1 – 2700 ppm) contents and minor concentrations of CO2 (0.5 – 11.2 %). The isotopic composition of TDC evidences an almost organic contribution. The only exception is represented by the CO2-richest sample where a small but significant mantle contribution is found. Such contribution can also be evidenced in its 3He rich isotopic composition. Further three samples of this group evidence a small mantle contribution. These samples were collected in the northern part of the basin along the main tectonic structures delimiting the basin and close to areas with quaternary volcanic activity. A second group is composed by two dissolved gases collected from deep boreholes (> 1200 m depth). Their composition is typical of hydrocarbon reservoirs being very rich in CH4 (> 78 %) and N2 (> 13%). Also the water composition is typical of saline connate waters (Cl- and B-rich, SO4-poor). C-isotopic composition of methane ( 13C -65% ) points to a biogenic origin while He-isotopic composition indicates a prevailing crustal signature for one (R/Ra 0.16) of the sites and small mantle contribution for the other (R/Ra 0.98). To the last group belong four gas samples taken at two sites within the ophiolitic basement that crops out west of the basin. These gases have the characteristic composition of gas generated by low temperature serpentinisation processes with high hydrogen (37 – 50 %) and methane (10 – 61 %) concentrations. While all gases show an almost identical D-H2 of -750h those of one of the two sites display an isotopic composition of methane ( 13C -5h D -105% ) and a C1/[C2+C3] ( 100) ratio typical of abiogenic hydrocarbons and mantle-type helium (R/Ra: 1.33), while those of the other site evidence a contribution of a crustal (thermogenic) component ( 13C-CH4 -30h D -325h C1/[C2+C3] 3000). Such crustal contribution is also supported by higher N2 contents (40% instead of 2%) and lower He-isotopic composition (R/Ra 0.07). The preliminary results highlight contributions of mantle-derived volatiles to the fluids vented along the Amik Basin. The main tectonic structure of the area, the Death Sea Fault, and other parallel structures crossing the basin seem to be the responsible for deep-originated volatiles drainage towards shallow levels.

The importance of methanotrophic activity in geothermal soils of Pantelleria island (Italy)

Sun, 07 Apr 2013 22:00:00 GMT

Title: The importance of methanotrophic activity in geothermal soils of Pantelleria island (Italy) Authors: D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Gagliano, A.L.; Università di Palermo, Dipartimento DiSTeM; Quatrini, P.; Università di Palermo, Dipartimento STEBICEF; Parello, F.; Università di Palermo, Dipartimento DiSTeM Abstract: Methane is a major contributor to the greenhouse effect, its atmospheric concentration being more than doubled since the XIX century. Every year 22 Tg of methane are released to the atmosphere from several natural and anthropogenic sources. Natural sources include geothermal/volcanic areas but the estimation of the total methane emission from these areas is currently not well defined since the balance between emission through degassing and microbial oxidation within the soils is not well known. Microbial oxidation in soils contributes globally for about 3-9% to the removal of methane from the atmosphere and recent studies evidenced methanotrophic activity also in soils of volcanic/geothermal areas despite their harsh environmental conditions (high temperatures, low pH and high concentrations of H2S and NH3). Methanotrophs are a diverse group of bacteria that are able to metabolize methane as their only source of carbon and energy and are found within the Alpha and Gamma classes of Proteobacteria and within the phylum Verrucomicrobia. Our purpose was to study the interaction between methanotrophic communities and the methane emitted from the geothermally most active site of Pantelleria island (Italy), Favara Grande, whose total methane emission has been previously estimated in about 2.5 t/a. Laboratory incubation experiments with soil samples from Favara Grande showed methane consumption values of up to 9500 ng g-1 dry soil per hour while soils collected outside the geothermal area consume less than 6 ng g-1 h-1. The maximum consumption was measured in the shallowest part of the soil profile (1-3 cm) and high values (>100 ng g-1 h-1) were maintained up to a depht of 15 cm. Furthermore, the highest consumption was measured at 37 C, and a still recognizable consumption (>20 ng g-1 h-1) at 80 C, with positive correlation with the methane concentration in the incubation atmosphere. These results can be considered a clear evidence of the presence of methanotrophs that were investigated by culturing and culture-independent techniques. The diversity of proteobacterial methanotrophs was investigated by creating a clone library of the amplified methane mono-oxygenase encoding gene, pmoA. Clone sequencing indicates the presence of Gammaproteobacteria in the soils of Favara Grande. Enrichment cultures, on a mineral medium in a CH4-enriched atmosphere, led to the isolation of different strains that were identified as Methylocistis spp., which belong to the Alphaproteobacteria. The presence of Verrucomicrobia was detected by amplification of pmoA gene using newly designed primers. Soils from Favara Grande show therefore the largest spectrum of methanotrophic microorganisms until now detected in a geothermal environment. While the presence of Verrucomicrobia in geothermal soils was predictable due to their thermophilic and acidophilic character, the presence of both Alpha and Gamma proteobacteria was unexpected. Their presence is limited to the shallowest part of the soil were temperatures are lower and is probably favored by a soil pH that is not too low (pH 5) and their contribution to biological methane oxidation at Pantelleria is significant. Understanding the ecology of methanotrophy in geothermal sites will increase our knowledge of the role of soils in methane emissions in such environments.

The fluids’ geochemistry along the "Sperchios Basin - Northern Evoikos Gulf" Graben, a geodynamically complex area of Central Greece

Sun, 07 Apr 2013 22:00:00 GMT

Title: The fluids’ geochemistry along the "Sperchios Basin - Northern Evoikos Gulf" Graben, a geodynamically complex area of Central Greece Authors: D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Bellomo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Calabrese, S.; Università di Palermo, Dipartimento DiSTeM; Kyriakopoulos, K.; University of Athens, Dept. Geology and Geoenvironment, Greece Abstract: The study area is a 130 km long fast spreading graben in Central Greece. Its complex geodynamical setting includes both the presence at depth of a subduction slab responsible for the recent (Quaternary) volcanic activity in the area and the western termination of a tectonic lineament of regional importance (the North-Anatolian fault). Its high geothermal gradient is evidenced by the presence of many thermal springs with temperatures from 19 to 82 C, issuing along the normal faults bordering the graben. In the period 2004-2012 about 50 gas and water samples have been collected and their chemical and isotopic analysis revealed a wide range of compositions. Going from west to east the gas composition changes from CH4- to CO2-dominated passing through mixed N2- CH4 and N2-CO2 compositions, while at the same time the He isotopic composition goes from typical crustal values (0.05 R/Ra) up to 0.87 R/Ra (corrected for air contamination), showing in the easternmost sites a small but significant mantle input. Isotopic composition of CH4-C indicates a thermogenic origin for the CH4-rich samples and hydrothermal origin for the remaining samples. Positive 15N values indicate a contribution of crustal derived nitrogen for the N2-rich samples. The 13C values of most the CO2-enriched samples show a mixed origin (mantle and marine carbonates). Also the chemical composition of the waters shows differences along the graben and two main groups can be separated. The first, represented by dilute waters (E.C. < 600 S/cm), is found in the westernmost sites characterised by the presence of CH4-rich and mixed N2-CH4 gases. The remaining waters display higher salinities (E.C. from 12 to 56 mS/cm) due to the mixing with a modified marine component. Only the water composition of easternmost sites in the Giggenbach’s cation triangular graph plots in the field of the partially equilibrated waters giving estimated temperatures at depth of 150-160 C.

Intermediate-field hydrogeological response induced by L'Aquila earthquake: the Acque Albule hydrothermal system (Central Italy)

Sat, 31 Dec 2011 23:00:00 GMT

Title: Intermediate-field hydrogeological response induced by L'Aquila earthquake: the Acque Albule hydrothermal system (Central Italy) Authors: La Vigna, F.; Università degli Studi Roma Tre; Carucci, V.; Università degli Sudi dell'Aquila; Mariani, I.; Università degli Studi Roma Tre; Minelli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pascale, F.; Università degli Studi Roma Tre; Mattei, M.; Università degli Studi Roma Tre; Mazza, R.; Università degli Studi Roma Tre; Tallini, M.; Università degli Sudi dell'Aquila Abstract: The intermediate-field hydrological response to the 6th April 2009 L’Aquila earthquake (Mw 6.3) has been studied using groundwater level data that were recorded by six piezometers in the Acque Albule Basin (Tivoli travertine quarry area) and in the Cornicolani Mountains (Pozzo del Merro shaft). The hydrogeological setting of the Tivoli area is characterised by two superimposed aquifers: a deep aquifer in carbonate and a shallow aquifer in travertine. At the time of the L’Aquila earthquake, the groundwater level at five piezometers located in the travertine quarry area began to decrease, while the water level slightly increased in the Pozzo del Merro karst lake that is located in the carbonate aquifer. To explain these variations, a possible conceptual model is proposed that assumes that ground - water-level variations are caused by a change in aquifer permeability principally due to the dynamic stress associated with the passing of the earthquake’s seismic waves.

The Deep Sea and Sub-Seafloor Frontier

Sat, 31 Dec 2011 23:00:00 GMT

Title: The Deep Sea and Sub-Seafloor Frontier Authors: Kopf, A.; MARUM, Univ. Bremen Leobener Strasse 28359 Bremen, Germany; Camerlenghi, A.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Trieste; Canals, M.; Departament d’Estratigrafia, Paleontologia i Geociències Marines de la Facultat de Geologia de la Universitat de Barcelona; Ferdelman, T.; Department of Biogeochemistry at the Max-Plank-Institute for Marine Microbiology, University of Bremen; Mevel, C.; Institut de Physique du Globe de Paris; Pälike, H.; The National Oceanography Centre, University of Southampton; Roest, W.; Unitè Gèosciences Marines Laboratoire Gèophysique et Gèodynamique Centre Bretagne - ZI de la Pointe du Diable - CS 10070 - 29280 Plouzané; Ask, M.; Rock Mechanics and Mining Engineering, 2006, Luleå University of Technology, Sweden; Barker-Jørgensen, B.; MPI for Marine Microbiology Celsiusstr. 1 D-28359 Bremen Germany; Boetius, A.; HGF-MPG Group for Deep Sea Ecology and Technology, Max Planck Institute for Marine Microbiology Celsiusstr. 1, 28359 Bremen, Germany; De Santis, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Früh-Green, G.; Inst. f. Geochemie und Petrologie, NW E 76.2, Clausiusstrasse 25, 8092 Zuerich Abstract: The deep sea and its sub-seafloor contain a vast reservoir of physical, mineral and biological resources that are rapidly coming into the window of exploitation. Assessing the opportunities and the risks involved requires a serious commitment to excellent deep sea research. There are numerous areas in this field in which Europe has cutting-edge technological potential. These include drilling and monitoring technology in the field of renewable energies such as geothermal, offshore wind and seafloor resources. Scientific ocean drilling will continue to play a valuable role, for example in the exploration of resource opportunities, in obtaining estimates for ecosystem and Earth climate sensitivity, or in improving understanding about the controlling factors governing processes and recurrence intervals of submarine geohazards. In Europe, there is also the scientific expertise needed to define a framework for policymakers for environmental protection measures and to carry out ecological impact assessments before, during and after commercial exploitation. Taking up these societal challenges will strengthen European scientific and educational networks and promote the development of world-class technology and industrial leadership.

Integrating geologic fault data into tsunami hazard studies

Thu, 18 Apr 2013 22:00:00 GMT

Title: Integrating geologic fault data into tsunami hazard studies Authors: Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Tiberti, M. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Kastelic, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Romano, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Piatanesi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Selva, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Lorito, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: We present the realization of a fault-source data set designed to become the starting point in regional-scale tsunami hazard studies. Our approach focuses on the parametric fault characterization in terms of geometry, kinematics, and assessment of activity rates, and includes a systematic classification in six justification levels of epistemic uncertainty related with the existence and behaviour of fault sources. We set up a case study in the central Mediterranean Sea, an area at the intersection of the European, African, and Aegean plates, characterized by a complex and debated tectonic structure and where several tsunamis occurred in the past. Using tsunami scenarios of maximum wave height due to crustal earthquakes (Mw=7) and subduction earthquakes (Mw=7 and Mw=8), we illustrate first-order consequences of critical choices in addressing the seismogenic and tsunamigenic potentials of fault sources. Although tsunamis generated by Mw=8 earthquakes predictably affect the entire basin, the impact of tsunamis generated by Mw=7 earthquakes on either crustal or subduction fault sources can still be strong at many locales. Such scenarios show how the relative location/orientation of faults with respect to target coastlines coupled with bathymetric features suggest avoiding the preselection of fault sources without addressing their possible impact onto hazard analysis results.

Different types of sediment gravity flows detected in the Var submarine canyon (northwestern Mediterranean Sea)

Tue, 18 Sep 2012 22:00:00 GMT

Title: Different types of sediment gravity flows detected in the Var submarine canyon (northwestern Mediterranean Sea) Authors: Khripounoff, A.; Ifremer; Crassous, P.; Ifremer; Lo Bue, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Dennielou, B.; Ifremer; Silva Jacinto, R.; Ifremer Abstract: Current velocities and vertical sediment fluxes in the Var submarine canyon were assessed at three stations respectively at 800 m, 1200 m and 1800 m depth, using moorings deployed for 4 months during winter 2008–2009. During this period, we observed three major sediment gravity flows, all characterized by sudden increases in current velocity that lasted 2–5 h and by downward particle fluxes. Each gravity flow, described using a high frequency current meter and two Acoustic Doppler Current Profiler (75 and 300 kHz ADCP) showed distinctive features. The first event, triggered during a flood of the Var River, was determined to be a hyperpycnal current with a large vertical extent (>100 m high) and relatively low velocity (40 cm s 1). The second event, observed after a Var River flood, was more energetic with a maximum horizontal current peak of 60 cm s 1 but with a low vertical extent (30 m high). This event was considered to be a turbidity landslide. The third was the result of a local canyon wall failure. It was characterized by a speed of >85 cm s 1. These peaks of current speed were associated with large clouds of material that transported sediment along the canyon and reached up to 200 g m 2 d 1 of sediment (>1 g m 2 d 1 of organic carbon). Our measurements in the Var canyon show the important role of gravity flows transporting particulate matter to the deep-sea floor. These large inputs of sediment and organic carbon may have a significant impact on deep-sea carbon storage in the Mediterranean Sea.