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  • 1
    Publication Date: 2021-12-13
    Description: Volcanic lake research boosted after lethal gas burst occurred at Lake Nyos (Cameroon) in 1986, a limnic rather than a volcanic event. This led to the foundation of the IAVCEI-Commission on Volcanic Lakes, which grew out into a multi-disciplinary scientific community since the 1990s. We here introduce the first data base of volcanic lakes VOLADA, containing 474 lakes, a number that, in our opinion, is surprisingly high. VOLADA could become an interactive, open-access working tool where our community can rely on in the future. Many of the compiled lakes were almost unknown, or at least unstudied to date, whereas there are acidic crater lakes topping active magmat- ic–hydrothermal systems that are continuously or discontinuously monitored, providing useful information for volcanic surveillance (e.g., Ruapehu, Yugama, Poás). Nyos-type lakes, i.e. those hosted in quiescent volcanoes and characterized by significant gas accumulation in bottom waters, are potentially hazardous. These lakes tend to remain stably stratified in tropical and sub-tropical climates (meromictic), leading to long-term build- up of gas, which can be released after a trigger. Some of the unstudied lakes are possibly in the latter situation. Acidic crater lakes are easily recognized as active, whereas Nyos-type lakes can only be recognized as potentially hazardous if bottom waters are investigated, a less obvious operation. In this review, research strategies are lined out, especially for the “active crater lakes”. We make suggestions for monitoring frequency based on the principle of the “residence time dependent monitoring time window”. A complementary, multi-disciplinary (geochemis- try, geophysics, limnology, statistics) approach is considered to provide new ideas, which can be the bases for fu- ture volcanic lake monitoring. More profound deterministic knowledge (e.g., precursory signals for phreatic eruptions, or lake roll-over events) should not only serve to enhance conceptual models of single lakes, but also serve as input parameters in probabilistic approaches. After more than 25 years of pioneering studies on rather few lakes (~20% of all), the scientific community should be challenged to study the many poorly studied volcanic lakes, in order to better constrain the related hazards.
    Description: Published
    Description: 78-97
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Volcanic lakes ; Active crater lakes ; Nyos-type lakes ; Monitoring ; Residence time dependent monitoring time window ; Hazard forecasting ; VOLADA data base ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2024-05-09
    Description: Real-time measurements of GEM and H2S discharged fromnatural and anthropogenic sources are a valuable tool to investigate the dispersion dynamics of these contaminants in air. In this study, a new approach to measure GEM and H2S concentrations in air, carried out by coupling a portable Zeeman atomic absorption spectrometer with high frequency modulation of light polarization (Lumex RA-915M) and a pulsed fluorescence gas analyzer (Thermo Scientific Model 450i), was applied to two distinct areas: (i) in the surroundings of Piancastagnaio (Siena, Central Italy), located in the eastern flanks ofMt. Amiata (a 200,000 years old volcano), where three geothermal plants are operating and whose exhaust gases are dispersed in the atmosphere after passing through the turbines and an abatement system to mitigate the environmental impact on air, and (ii) at Solfatara Crater (Campi Flegrei, Southern Italy), a volcanic apparatus characterized by intense hydrothermal activity. In 2014, seven GEMand H2S surveys were carried out in the two areas along pre-defined pathways performed by car at both the study sites. The lowest and highest recorded GEM and H2S concentrations at Piancastagnaio were up to 194 and 77 ng/m3, respectively, whilst at Solfatara Crater were up to 690 and 3392 μg/m3, respectively. Although the GEM concentrations at Piancastagnaio were lower than the limit value recommended by local regulations for outdoor environment (300 ng/m3), they were almost one order of magnitude higher than the GEM background both in Tuscany (~3.5 ng/m3) and Mt. Amiata (3–5 ng/m3), suggesting that the main source of GEM was likely related to the geothermal plants. At Solfatara Crater, the highest GEM values were recognized in proximity of the main fumarolic gas discharges. As far as the H2S concentrations are concerned, the guideline value of 150 μg/m3, recommended by WHO (2000), was frequently overcome in the study areas. Dot (in the surroundings of Piancastagnaio) and contour (at Solfatara Crater) maps for GEM and H2S concentrations built for each survey highlighted the important effects played by the meteorological parameters, the latter being measured by a Davis® Vantage Vue weather station. In particular, the GEM and H2S plumes were strongly affected by the wind speed and direction thatwere able to modify the dispersion of the two parameters in air in a matter of hours, indicating that the proposed analytical approach is able to produce a more realistic picture of the distribution of these air pollutants than that provided by using passive traps. Finally, the H2S/GEMratio, calculated by normalizing the measured GEM and H2S concentrations to their highest values (nH2S/GEM),was used as a good proxy for the chemical-physical processes that these two gas species can suffer once emitted in the air. In particular, H2S resulted to be more affected by secondary processes than GEM, possibly related to photochemical oxidation reactions.
    Description: Published
    Description: 48-58
    Description: 4V. Vulcani e ambiente
    Description: JCR Journal
    Description: restricted
    Keywords: Real-time measurements ; gaseous elemental mercury ; Hydrogen sulphide ; Gaseous contaminants ; Solfatara crater ; Mt. Amiata ; 01. Atmosphere::01.01. Atmosphere::01.01.03. Pollution ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2024-05-09
    Description: In this study, hydrogen sulfide (H2S) measurements in air carried out using (a) passive/diffusive samplers (Radiello® traps) and (b) a high-frequency (60 s) real-time analyzer (Thermo® 450i) were compared in order to evaluate advantages and limitations of the two techniques. Four different sites in urban environments (Florence, Italy) and two volcanic areas characterized by intense degassing of H2S-rich fluids (Campi Flegrei and Vulcano Island, Italy) were selected for such measurements. The concentrations of H2S generally varied over 5 orders of magnitude (from 10 1e103 mg/m3), the H2S values measured with the Radiello® traps (H2SR) being significantly higher than the average values measured by the Thermo® 450i during the trap exposure (H2STa), especially when H2S was 〈30 mg/m3. To test the reproducibility of the Radiello® traps, 8 passive/diffusive samplers were contemporaneously deployed within an 0.2 m2 area in an H2S-contaminated site at Mt. Amiata (Tuscany, Italy), revealing that the precision of the H2SR values was ±49%. This large uncertainty, whose cause was not recognizable, is to be added to that related to the environmental conditions (wind speed and direction, humidity, temperature), which are known to strongly affect passive measurements. The Thermo® 450i analyzer measurements highlighted the occurrence of short-term temporal variations of the H2S concentrations, with peak values (up to 5732 mg/m3) potentially harmful to the human health. The Radiello® traps were not able to detect such temporal variability due to their large exposure time. The disagreement between the H2SR and H2STa values poses severe concerns for the selection of an appropriate methodological approach aimed to provide an accurate measurement of this highly toxic air pollutant in compliance with the WHO air quality guidelines. Although passive samplers may offer the opportunity to carry out low-cost preliminary surveys, the use of the high-frequency H2S analyzer is preferred when an accurate assessment of air quality is required. In fact, the latter provides precise real-time measurements for a reliable estimation of the effective exposure to hazardous H2S concentrations, giving insights into the mechanisms regulating the dispersion of this air pollutant in relation to the meteorological parameters.
    Description: Published
    Description: 51-58
    Description: 4V. Vulcani e ambiente
    Description: JCR Journal
    Description: restricted
    Keywords: active analysers ; Passive/diffusive samplers ; Gaseous contaminants ; Air quality monitoring ; Hydrogen sulphide ; 01. Atmosphere::01.01. Atmosphere::01.01.03. Pollution ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 01. Atmosphere::01.01. Atmosphere::01.01.08. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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