Gas Emissions From the Western Aleutians Volcanic Arc

The Aleutian Arc is remote and highly active volcanically. Its 4,000 km extent from mainland Alaska to Russia’s Kamchatka peninsula hosts over 140 volcanic centers of which about 50 have erupted in historic times. We present data of volcanic gas samples and gas emission measurements obtained during an expedition to the western-most segment of the arc in September 2015 in order to extend the sparse knowledge on volatile emissions from this remote but volcanically active region. Some of the volcanoes investigated here have not been sampled for gases before this writing. Our data show that all volcanoes host high-temperature magmatic-hydrothermal systems and have gas discharges typical of volcanoes in oceanic arcs. Based on helium isotopes, the western Aleutian Arc segment has minimal volatile contributions from the overriding crust. Volcanic CO2 fluxes from this arc segment are small, compared to the emissions from volcanoes on the Alaska Peninsula and mainland Alaska. The comparatively low CO2 emissions may be related to the lower sediment flux delivered to the trench in this part of the arc.

Empirical dependence of the probability of blocks rotations on the diffusion coefficient in a cellular automaton with a Margolus neighbourhood

The paper considers a cellular automaton approach to modeling physical processes, in particular, the diffusion of pulsed periodic gas discharges in plasma. An attempt to determine the dependence of the probability of the block rotation on the diffusion coefficient for a cellular automaton diffusion model with a Margolus neighborhood is describe. Some features of the tensor approach to the implementation of random block cellular automata are described. The results of computer experiments are presented. The analysis of this results indicates that the data from the literature sources differ from the data obtained during the experiment.

Electron impact dissociation of CO2 (a review)

Based on a detailed analysis and generalization of the results of calculations of the energy spectrum of electrons using different models in gas discharges in pure carbon dioxide CO2 and in mixtures containing CO2 , the rate constant of CO2 dissociation by electron impact in a gas discharge of direct current at atmospheric pressure is found. It is shown that, at values of the reduced electric field from 55 Td to 100 Td, the predominant mechanism of decomposition of the CO2 molecule is the collision of CO2 molecules with electrons. An expression is obtained for calculating the rate constant of CO2 dissociation by electron impact as a function of the reduced electric field.

Plasma bubbles: a route to sustainable chemistry

Atmospheric plasma discharges are finding increased applications in addressing environmental challenges including water purification, chemical synthesis and biotechnology. An effective means of interfacing the reactivity of plasma gas discharges with liquids is needed to enhance liquid phase chemical reactions. Plasma discharges in bubbles has been considered as an innovative solution for achieving this goal potentially offering electrically driven, sustainable chemistry with low energy consumption and the unique benefit of maintaining a large volume discharge under the liquid surface. Here we provide a concise review on the state-of-art for research on plasma-bubble interactions and a perspective for future research.

The Rome gas blowout zone (Central Italy)

<p>Colli Albani is an alkali-potassic quiescent volcano of Central Italy that last erupted 36 ka ago. Several lahar generating water overflows have occurred from Albano crater lake, the most recent in Roman times (IV Century B.P.) and the resulting deposits form a surficial impermeable cover on its north-western flank. An important NW-SE trending volcano-tectonic fracture extends from the volcano to the periphery of Rome city. This is a leaky fracture allowing deep magmatic gas to rise toward the surface. In zones where the impervious cover has been removed by excavations, as Cava dei Selci, the gas is freely discharged into the atmosphere creating local hazardous conditions. Elsewhere, the gas dissolves and pressurizes the shallow aquifer confined underneath the impervious cover. Any time this aquifer is reached by a drilling, a dangerous gas blowout may be generated, i.e. a sudden emission of a jet of gas, nebulized water and fine loose fragments of volcanic rocks. Since 2003 four gas blowouts, from ~ 45–50 m deep drillings, have occurred at the boundary between Rome and Ciampino municipalities, a site designed as the Rome gas blowout zone. Dangerous atmospheric CO<sub>2</sub> and H<sub>2</sub>S concentrations killed some animals and several families had to be evacuated because of hazardous gas concentration inside their houses. The emitted gas consists mostly of CO<sub>2</sub> (>90 vol.%) and contains a low but significant quantity of H<sub>2</sub>S (0.3–0.5 vol.%); it has the highest helium isotopic R/Ra value (up to 1.90) of all Colli Albani natural gas discharges. This He isotopic value is similar or even slightly higher than in the fluid inclusions of phenocrysts of the Colli Albani volcanic rocks, suggesting a likely magmatic origin of the gas. Colli Albani volcano is characterized by anomalous uplift, release of magmatic gas and episodic seismic crises. The Rome gas blowouts represent a geochemical window to investigate deep volcanic processes. Should a volcanic unrest occur, gas hazard would increase in this densely inhabited zone, as the input of magmatic gas into the confined aquifer might create overpressure conditions leading to a harmful phreatic explosion, or increase the emission of hazardous gas through newly created fractures.</p>