Search results for "LCA"
showing 10 items of 1995 documents
Constraints on mantle source and interactions from He-Sr isotope variation in Italian Plio-Quaternary volcanism.
2008
[1] Helium isotope ratios of olivine and pyroxene phenocrysts from Plio-Quaternary volcanic rocks from southern Italy (seven Aeolian Islands, Mt. Vulture, Etna, Ustica, and Pantelleria) range from 2.3 to 7.1 Ra. Importantly, the phenocryst 3He/4He correlate well with whole rock Sr isotopic composition (0.70309– 0.70711), reflecting the mixing of two sources. A significant contribution of He from crustal contamination is recorded only occasionally (e.g., pyroxenes from Vulcano). When merged with data from the Roman Comagmatic Province, a remarkably strong near-linear He-Sr isotope correlation is apparent. The general northward decrease in 3He/4He corresponds to an increase in 87Sr/86Sr (and …
The heterogeneity of the Mexican lithospheric mantle: Clues from noble gas and CO2 isotopes in fluid inclusions
2022
The abundance of mantle-derived rocks and lavas, in combination with its tectonic evolution, render Mexico a perfect laboratory to investigate the chemical and the isotopic heterogeneity of the lithospheric mantle. New data on the composition of noble gases and CO2in Mexican mantle xenoliths and lavas is reported. Our samples consist of six ultramafic nodules from the Durango Volcanic Field (DVF) and the San Quintin Volcanic Field (SQVF), monogenetic complexes belonging to the Mexican Basin and Range province; and four lavas from the Sierra Chichinautzin (SCN), a Quaternary monogenetic volcanic field located in the Mexican volcanic arc. Ne and Ar isotopes in fluid inclusions reveal mixing b…
Isolation, characterization and determination of biotechnological potential of oil-degrading bacteria from Algerian centre coast
2019
Aims The Algerian coastline is exposed to several types of pollution, including hydrocarbons. The aim of this work was to isolate oil-degrading bacteria and to explore the intrinsic bioremediation potential of part of its contaminated harbour. Methods and results A collection of 119 strains, capable to grow on mineral medium supplemented with hydrocarbons, were obtained from polluted sediment and seawater collected from Sidi Fredj harbour (Algiers). Twenty-three strains were selected for further studies. Sequencing of the 16S rRNA gene showed that most isolates belong to genera of hydrocarbonoclastic bacteria (Alcanivorax), generalist hydrocarbons degraders (Marinobacter, Pseudomonas, Gordo…
Preliminary geochemical characterization of gas manifestations in North Macedonia
2020
<p>Like most of the Balkan Peninsula, North Macedonia is a geodynamically active area. As such it has many hydrothermal features and gas manifestations. Until now, no systematic study about the geochemical characterization of the geogenic gases was made before in this country. In August 2019, 24 gas samples were collected in the study area. All, except one collected at Duvalo (soil gas), are gases bubbling or dissolved in thermomineral waters (temperatures from 12 to 66 °C). They were analysed in the laboratory for their chemical (He, Ne, Ar, O<sub>2</sub> , N<sub>2</sub> , H<sub>2</sub&…
Mineralogy of the soils altered by fumarolic activity at Nisyros volcano, Greece
2017
Nisyros is the easternmost island of the South Aegean Active Volcanic arc in Greece. It is an active stratovolcano known for its intense hydrothermal activity. In this study we present the results of the mineralogical analyses of 20 soil samples collected in the caldera area. Samples were analysed through X-ray diffraction and the results allow us to divide them in two groups: Lakki Plain and Stefanos Crater. In their majority the soils of Lakki Plain have a main mineralogical assemblage that consists of quartz, feldspar and gismondine (Ca2Al4Si4O16·9H2O). Gismondine as well as stellerite (CaAl2Si7O18·7H2O), which is appearing in some samples, derive from hydrothermal alteration, whilst wol…
Active real-time analyzers vs. passive/diffusive samplers for hydrogen sulfide (H2S) in air: a critical comparison
2015
Hydrogen sulfide (H2S) is a gas pollutant discharged in air from a large number of natural and anthropogenic sources. Its peculiar rotten-egg smell, causing odor nuisance to neighboring communities, is detectable at concentrations between 0.7 and 42 μg/m3 (Schiffman & Williams, 2005). High H2S concentrations could cause eye irritation, damage to the upper respiratory apparatus and loss of smell. The effects of long-term low level (< 2,800 μg/m3) exposures to H2S are still matter of debate (Bates et al., 2013). Hence, the development of techniques for accurate measurements of H2S in air at a wide range of concentrations is a primary issue in environmental monitoring. Two different app…
Hazard connected to endogenous gas emissions in Greece
2016
Like other geodynamically active areas, Greece is also affected by a large number of geogenic gas manifestations that occur either in form of point sources (fumaroles, mofettes, bubbling gases) or as diffuse soil gas emanations. Geogenic sources could have strong impact on human health. CO2 and H2S are the main gases responsible for acute mortality due to their asphyxiating and/or toxic properties. Gas hazard is often disregarded because in fatal episodes the death cause is often not correctly attributed. Geodynamic active areas can release geogenic gases for million years over wide areas and it is therefore important not to underestimate potential risks. A preliminary estimation of the gas…
Risks related to gas manifestations in the Hellenic territory
2015
Like other geodynamically active areas, Greece is affected by a large number of geogenic gas manifestations. These occur either in form of point sources (fumaroles, mofettes, bubbling gases) or as diffuse emanations. We produced a catalogue of the geogenic gas manifestations of Greece also considering few literature data. Collected samples were analysed for their chemical (He, Ne, Ar, O2, N2, H2, H2S, CO, CH4 and CO2) and isotopic composition (He, C and N). Geogenic gases, apart from having important influences on the global climate, could have strong impact on human health. Gas hazard is often disregarded because fatal episodes are often not correctly attributed. Geodynamic active areas re…
Insights on Hydrothermal‐Magmatic Interactions and Eruptive Processes at Poás Volcano (Costa Rica) From High‐Frequency Gas Monitoring and Drone Measu…
2019
Texto completo del documento Identification of unambiguous signals of volcanic unrest is crucial in hazard assessment. Processes leading to phreatic and phreatomagmatic eruptions remain poorly understood, inhibiting effective eruption forecasting. Our 5‐year gas record from Poás volcano, combined with geophysical data, reveals systematic behavior associated with hydrothermal‐magmatic eruptions. Three eruptive episodes are covered, each with distinct geochemical and geophysical characteristics. Periods with larger eruptions tend to be associated with stronger excursions in monitoring data, particularly in SO2/CO2 and SO2 flux. The explosive 2017 phreatomagmatic eruption was the largest erupt…
Volcanic gas monitoring of quiescent volcanoes using permanent Multi-GAS networks
2014
The Multi-component Gas Analyzer System (Multi-GAS) has recently consolidated as a standard technique for the nearly real-time in-situ observation of major volcanogenic components (H2O, CO2, SO2, H2S,H2) in volcanic gas plumes. The Multi-GAS has been initially operated at open-vent volcanoes, where it has revealed ideal for long-term continuous observations at for instance Etna and Stromboli volcanoes in Italy, therein paving the way to the acquisition of unprecedentedly long and continuous volcanic gas time-series. We here initially review the present state of the expanding network of permanent Multi-GAS instruments, now covering about 10 volcanoes worldwide. We then specifically focus on …