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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)

2013-04-22T22:00:00Z

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.

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

2013-04-07T22:00:00Z

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)

2013-04-07T22:00:00Z

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

2013-04-07T22:00:00Z

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.

Strengthening of the hydrological cycle in future scenarios: atmospheric energy and water balance perspective

2011-12-31T23:00:00Z

Title: Strengthening of the hydrological cycle in future scenarios: atmospheric energy and water balance perspective Authors: Alessandri, A.; ENEA; Fogli, P. G.; CMCC; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Zeng, N.; University of Mariland Abstract: Future climate scenarios experiencing global warming are expected to strengthen the hydrological cycle during the 21st century (21C). We analyze the strengthening of the global-scale increase in precipitation from the perspective of changes in whole atmospheric water and energy balances. By combining energy and water equations for the whole atmosphere, we obtain constraints for the changes in surface fluxes and partitioning at the surface between sensible and latent components. We investigate the differences in the strengthening of the hydrological cycle in two centennial simulations performed with an Earth system model forced with specified atmospheric concentration pathways. Alongside the Special Report on Emissions Scenario (SRES) A1B, which is a medium-high non-mitigation scenario, we consider a new aggressive-mitigation scenario (E1) with reduced fossil fuel use for energy production aimed at stabilizing global warming below 2 K. Our results show that the mitigation scenario effectively constrains the global warming with a stabilization below 2 K with respect to the 1950–2000 historical period. On the other hand, the E1 precipitation does not follow the temperature field toward a stabilization path but continues to increase over the mitigation period. Quite unexpectedly, the mitigation scenario is shown to strengthen the hydrological cycle even more than SRES A1B till around 2070. We show that this is mostly a consequence of the larger increase in the negative radiative imbalance of atmosphere in E1 compared to A1B. This appears to be primarily related to decreased sulfate aerosol concentration in E1, which considerably reduces atmospheric absorption of solar radiation compared to A1B. The last decades of the 21C show a marked increase in global precipitation in A1B compared to E1, despite the fact that the two scenarios display almost the same overall increase of radiative imbalance with respect to the 20th century. Our results show that radiative cooling is weakly effective in A1B throughout the 21C. Two distinct mechanisms characterize the diverse strengthening of the hydrological cycle in the middle and end- 21C. It is only through a very large perturbation of surface fluxes that A1B achieves a larger increase in global precipitation in the last decades of the 21C. Our energy/water budget analysis shows that this behavior is ultimately due to a bifurcation in the Bowen ratio change between the two scenarios. This work warns that mitigation policies that promote aerosol abatement, may lead to an unexpected stronger intensification of the hydrological cycle and associated changes that may last for decades after global warming is effectively mitigated. On the other hand, it is also suggested that predictable components of the radiative forcing by aerosols may have the potential to effectively contribute to the decadal-scale predictability of changes in the hydrological strength.

Fluid geochemistry along the Eliki and Aigion seismogenic segments (Gulf of Corinth, Greece)

2013-03-20T23:00:00Z

Title: Fluid geochemistry along the Eliki and Aigion seismogenic segments (Gulf of Corinth, Greece) Authors: Pizzino, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Cinti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Galli, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: Three geochemical surveys in ground waters were carried out in the Selianitika–Trapeza area, Gulf of Corinth, with the main purposes: (1) to define the geochemical patterns of the circulating ground waters; (2) to discriminate the role of active fault systems in affecting the ground water chemistry and hydrogeology, exploiting geochemical techniques tested in other areas; (3) to select sites for the continuous geochemical surveillance of the tectonic activity of the area. A total of 50 sites have been sampled, and numerous chemical and stable isotope analyses have been performed. We identify three geochemical active fault zones: (i) the Eliki–Nikolaikea area; (ii) the Selianitika–Rododafni–Nerazes area, and (iii) the Trapeza sector. The Nerazes well site and the Selianitika spa have been selected for exploiting a geochemical-hydrological monitoring surveillance of the tectonic activity.

Geochemistry of shallow aquifers and soil gas surveys in a feasibility study at the Rivara natural gas storage site (Po Plain, Northern Italy)

2012-12-31T23:00:00Z

Title: Geochemistry of shallow aquifers and soil gas surveys in a feasibility study at the Rivara natural gas storage site (Po Plain, Northern Italy) Authors: Sciarra, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Cinti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Pizzino, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Procesi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Voltattorni, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Mecozzi, S.; Earth Science Department, University of Modena and Reggio Emilia; Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: A geochemical survey, in shallow aquifers and soils, has been carried out to evaluate the feasibility of natural gas (CH4) storage in a deep saline aquifer at Rivara (MO), Northern Italy. This paper discusses the areal distribution of CO2 and CH4 fluxes and CO2, CH4, Rn, He, H2 concentrations both in soils and shallow aquifers above the proposed storage reservoir. The distribution of pathfinder elements such as 222Rn, He and H2 has been studied in order to identify potential faults and/or fractures related to preferential migration pathways and the possible interactions between the reservoir and surface. A geochemical and isotopic characterization of the ground waters circulating in the first 200 m has allowed to investigation of (i) the origin of the circulating fluids, (ii) the gas–water–rock interaction processes, (iii) the amount of dissolved gases and/or their saturation status. In the first 200 m, the presence of CH4-rich reducing waters are probably related to organic matter (peat) bearing strata which generate shallowderived CH4, as elsewhere in the Po Plain. On the basis of isotopic analysis, no hints of thermogenic CH4 gas leakage from a deeper reservoir have been shown. The d13C(CO2) both in ground waters and free gases suggests a prevalent shallow origin of CO2 (i.e. organic and/or soil-derived). The acquisition of preinjection data is strategic for the natural gas storage development project and as a baseline for future monitoring during the gas injection/withdrawing period. Such a geochemical approach is considered as a methodological reference model for future CO2/CH4 storage projects.

Are the Salinelle mud volcanoes threatening human health or are anthropogenic activities threatening the Salinelle mud volcanoes? A comment on “Trace element biomonitoring using mosses in urban areas affected by mud volcanoes around Mt. Etna. The case of the Salinelle, Italy” by Bonanno et al. (DOI 10.1007/s10661-011-2332-z)

2012-12-31T23:00:00Z

Title: Are the Salinelle mud volcanoes threatening human health or are anthropogenic activities threatening the Salinelle mud volcanoes? A comment on “Trace element biomonitoring using mosses in urban areas affected by mud volcanoes around Mt. Etna. The case of the Salinelle, Italy” by Bonanno et al. (DOI 10.1007/s10661-011-2332-z) 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 Abstract: no abstract

Discrimination between effects induced by microbial activity and water-rock interactions under hydrothermal conditions according to REE behaviour

2013-06-08T22:00:00Z

Title: Discrimination between effects induced by microbial activity and water-rock interactions under hydrothermal conditions according to REE behaviour Authors: Censi, P.; DiSTeM UniPA; Cangemi, M.; DiSTeM UniPA; Madonia, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Saiano, F.; AGROPa UniPA; Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Zuddas, P.; iSTeP Universitè P. er M. Curie Paris Abstract: Rare Earths (REE) were investigated in siliceous stromatolites forming in the Specchio di Venere Lake in Pantelleria Island. Chondrite-normalised patterns show significant La enrichments and Eu depletions suggesting that fluids involved in stromatolite growth experienced strong rock-water interactions under hydrothermal conditions. At the same time, enrichments of heavy REE (HREE), with respect to intermediate REE (MREE) suggest that hydrothermal fluids interacted with microbial mats during deposition of stromatolites. The above-mentioned features suggest that rock-water interactions and bacterial activity were simultaneously recorded in REE patterns of stromatolites and can be discriminated in terms of amplitudes of La anomaly and HREE/MREE ratio

Another kind of “volcanic risk”: the acidification of sea-water. Vulcano Island (Italy) a natural laboratory for ocean acidification studies

2012-12-11T23:00:00Z

Title: Another kind of “volcanic risk”: the acidification of sea-water. Vulcano Island (Italy) a natural laboratory for ocean acidification studies Authors: Boatta, F.; Università di Palermo, Dipartimento DiSTeM; D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Gagliano, L.; Università di Palermo, Dipartimento DiSTeM; Calabrese, S.; Università di Palermo, Dipartimento DiSTeM; Liotta, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Milazzo, M.; Università di Palermo, Dipartimento DiSTeM; Parello, F.; Università di Palermo, Dipartimento DiSTeM Editors: Corsaro, R.A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: Acidification of seawater is one of the aspect tightly linked to volcanic risk, due to the presence of submarine vents releasing abundant volcanic fluids. In aquatic system CO2 gas dissolves, hydrates and dissociates to form weak carbonic acid, which is the main driver of natural weathering reactions [Drever, 1997]. The result of the CO2 increase is seawater acidification. Vulcano Island, the southernmost of Aeolian Islands, is located in the Southern Tyrrhenian Sea (Italy), approximately 18 miles off the NE coast of Sicily. The Baia di Levante can be considered a natural laboratory where almost all of the biogeochemical processes related to the ocean acidification can be studied. In this area many submarine vents release CO2. Four geochemical surveys of the Bay were carried out in April - September 2011 and May - June 2012. The main physic-chemical parameters (T, pH, Eh, electric conductivity) were measured at more than 70 sites and more than 40 samples for chemical analyses were collected at representative points. Major (Na, K, Mg, Ca, Cl, SO4) and some minor components (B, Sr, Fe) and trace elements (Mn, Mo, Al, U, Ce, Pb, Tm, Tb, Nd, Th) dissolved in water, the chemical composition of dissolved gases (He, H2, O2, N2, CH4 and CO2) and the isotopic composition of total dissolved inorganic carbon were determined in the laboratory. The bubbling CO2 produces a strong decrease in pH from the normal seawater value of 8.2 down to 5.5 (Figure 1). In the area close to the main degassing vents, characterized by very low pH, macroorganisms were absent. Acidification of sea water is one of the aspect tightly linked to volcanic risk, due to the presence of submarine vents releasing abundant volcanic fluids. At Baia di Levante, about 300 m from the main vents the seawater is only slightly acidic (pH 6.5 - 7.0) resembling the ocean water conditions in equilibrium with the high atmospheric CO2 concentrations expected in the near future. Therefore environments like this, naturally enriched in CO2, are good laboratories to study the consequences of ocean acidification on aquatic biota [Doney et al., 2009]. Furthermore acidification is tightly linked with the mobility and bio-availability of heavy metals [Millero et al., 2009] in sea water and volcanoes were always the favourite choice for human settlements; as a consequence economic anthropological activity, such as fishing, could be dangerous for human health, because of the presence toxic level of trace metals in the food chain due to the presence of the volcano’s. The present study could provide important information about the best environmental management of volcanic areas such as Vulcano Island