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A previously undocumented shallow water hydrothermal field from Sicily (Southern Tyrrhenian Sea, Italy) is here described, based on a multidisciplinary investigation. The field, covering an area of nearly 8000 m2 and a depth from the surface to -5 m, was explored in June 2021 to characterise the main physico-chemical features of the water column, describe the bottom topography and features, and identify the main megabenthic and nektonic species. Twenty sites were investigated to characterise the carbonate system. Values of pH ranged between 7.84 and 8.04, ΩCa between 3.68 and 5.24 and ΩAr from 2.41 to 3.44. Geochemical analyses of hydrothermal gases revealed a dominance of CO2 (98.1%) together with small amounts of oxygen and reactive gases. Helium isotope ratios (R/Ra = 2.51) and δ13CCO2 suggest an inorganic origin of hydrothermal degassing of CO2 and the ascent of heat and deep-seated magmatic fluids to the surface. Visual census of fishes and megabenthos (mainly sessile organisms) allowed the identification of 64 species, four of which are protected by the SPA/BIO Protocol and two by the International Union for Conservation of Nature. The macroalgae Halopteris scoparia and Jania rubens and the sponge Sarcotragus sp. were the dominant taxa in the area, while among fishes Coris julis and Chromis chromis were the most abundant species. This preliminary investigation of San Giorgio vent field suggests that the site could be of interest and suitable for future experimental studies of ocean acidification. [ABSTRACT FROM AUTHOR]

Volcanic eruptions pose a major natural hazard influencing the environment, climate and human beings at different temporal and spatial scales. Nevertheless, several volcanoes worldwide are poorly monitored and assessing the impact of their eruptions remains, in some cases, challenging. Nowadays, different numerical dispersion models are largely employed in order to evaluate the potential effects of volcanic plume dispersion due to the transport of ash and gases. On 28 August 2019, both Mt. Etna and Stromboli had eruptive activity; Mt. Etna was characterised by mild-Strombolian activity at summit craters, while at Stromboli volcano, a paroxysmal event occurred, which interrupted the ordinary typical-steady Strombolian activity. Here, we explore the spatial dispersion of volcanic sulphur dioxide (SO 2 ) gas plumes in the atmosphere, at both volcanoes, using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) considering the ground-measured SO 2 amounts and the plume-height as time-variable eruptive source parameters. The performance of WRF-Chem was assessed by cross-correlating the simulated SO 2 dispersion maps with data retrieved by TROPOMI and OMI sensors. The results show a feasible agreement between the modelled dispersion maps and TROPOMI satellite for both volcanoes, with spatial pattern retrievals and a total mass of dispersed SO 2 of the same order of magnitude. Predicted total SO 2 mass for Stromboli might be underestimated due to the inhibition from ground to resolve the sin-eruptive SO 2 emission due to the extreme ash-rich volcanic plume released during the paroxysm. This study demonstrates the feasibility of a WRF-Chem model with time-variable ESPs in simultaneously reproducing two eruptive plumes with different SO 2 emission and their dispersion into the atmosphere. The operational implementation of this method could represent effective support for the assessment of local-to-regional air quality and flight security and, in case of particularly intense events, also on a global scale. [ABSTRACT FROM AUTHOR]

The Santa Barbara and Aragona areas are affected by mud volcanism (MV) phenomena, consisting of continuous or intermittent emission of mud, water and gases. This activity could be interrupted by paroxysmal events, with an eruptive column composed mainly of clay material, water and gases. They are the most hazardous phenomena and, nowadays, it is impossible to define the potential parameters for modeling the phenomenon. In 2017, two DSM were performed by drone in both areas, thus allowing the mapping of the emission zones and the covered areas by the previous events. Detailed information about past paroxysms was obtained from historical sources and, with the analysis of the 2017 DSMs, a preliminary hazard assessment was carried out, for the first time at two sites. Two potentially hazardous paroxysm surfaces of 0.12 km2 and 0.20 km2 for Santa Barbara and Aragona respectively, were defined. In May 2020, at Aragona, a new paroxysm covered a surface of 8,721 m2. After this, a new detailed DSM was collected with the aim to make a comparison with 2017 one. Since 2017, a seismic station was installed at Santa Barbara. From preliminary results, both seismic events and ambient noise showed a frequency of 5-10 Hz. [ABSTRACT FROM AUTHOR]

Lahars are a widespread phenomenon on Vulcano island (Italy), where many loose pyroclastic deposits provide a significant source of sediments. In this study we have estimated the volumes of tephra-fallout deposit that could be remobilized by rainfall-triggered lahars in association with two eruptive scenarios that have characterized the activity of La Fossa cone: a long-lasting Vulcanian cycle and a subplinian eruption. The spatial distribution and volume of tephra-fallout deposits that could potentially trigger lahars were analysed based on a combination of tephra-fallout probabilistic modelling (with TEPHRA2), slope stability modelling (with TRIGRS), field observations and geotechnical tests. Field characterization includes tephra-fallout primary deposits in the lahar initiation zones and lahar deposits both on the volcanic cone and in the ring plain. Model input data (hydraulic conductivity, friction angle, cohesion, total unit weight of the soil, saturated and residual water content) were obtained from both geotechnical tests and field measurements. In particular, hydraulic conductivity plays an important role on the stability of tephra-fallout deposits. Our parametric analysis has shown that the tephra-fallout critical thickness required to trigger a lahar for the considered rainfall event is between 20-25 cm for the Vulcanian scenario, and between 10-65 cm or < 10 cm for a subplinian event depending on the hydraulic conductivity. The scenario remobilizing the largest unstable volumes by rain-triggered lahars is, therefore, that associated with a Vulcanian cycle with duration of 18 months and a subplinian eruption of VEI 3 (for low hydraulic conductivity). TRIGRS simulations show that shallow landsliding is an effective process for eroding the primary tephra-fallout deposits in combination with high-intensity rainfall events with short duration, such as those occurring on Vulcano every year. Our results provide a new innovative treatment of the cascading effect between tephra fallout and lahar susceptibility that also accounts for detailed characterization of source sediments based on field observations and geotechnical tests. [ABSTRACT FROM AUTHOR]

A previously undocumented shallow water hydrothermal field from Sicily (Southern Tyrrhenian Sea, Italy) is here described, based on a multidisciplinary investigation. The field, covering an area of nearly 8000 m2 and a depth from the surface to -5 m, was explored in June 2021 to characterise the main physico-chemical features of the water column, describe the bottom topography and features, and identify the main megabenthic and nektonic species. Twenty sites were investigated to characterise the carbonate system. Values of pH ranged between 7.84 and 8.04, ΩCa between 3.68 and 5.24 and ΩAr from 2.41 to 3.44. Geochemical analyses of hydrothermal gases revealed a dominance of CO2 (98.1%) together with small amounts of oxygen and reactive gases. Helium isotope ratios (R/Ra = 2.51) and δ13CCO2 suggest an inorganic origin of hydrothermal degassing of CO2 and the ascent of heat and deep-seated magmatic fluids to the surface. Visual census of fishes and megabenthos (mainly sessile organisms) allowed the identification of 64 species, four of which are protected by the SPA/BIO Protocol and two by the International Union for Conservation of Nature. The macroalgae Halopteris scoparia and Jania rubens and the sponge Sarcotragus sp. were the dominant taxa in the area, while among fishes Coris julis and Chromis chromis were the most abundant species. This preliminary investigation of San Giorgio vent field suggests that the site could be of interest and suitable for future experimental studies of ocean acidification., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 D’Alessandro et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)