Volcanic Gas Hazard Assessment in the Baia di Levante Area (Vulcano Island, Italy) Inferred by Geochemical Investigation of Passive Fluid Degassing

Iole Serena Diliberto,Antonina Lisa Gagliano,Agnes Mazot,Antonino Pisciotta,Salvatore Inguaggiato,Mariana Patricia Jacome Paz,Maria Pedone,Marianna Cangemi,Paolo Madonia

doi:10.3390/geosciences11110478

Abstract

In a volcanic area, the composition of air is influenced by the interaction between fluids generated from many different environments (magmatic, hydrothermal, meteoric, and marine). Any physical and chemical variation in one of these subsystems is able to modify the outgassing dynamic. The increase of natural gas hazard, related to the presence of unhealthy components in air, may depend on temporary changes both in the pressure and chemical gradients that generate transient fluxes of gases and can have many different causes. Sometimes, the content of unhealthy gases approaches unexpected limits, without clear warning. In this case, an altered composition of the air can be only revealed after accurate sampling procedures and laboratory analysis. The investigations presented here are a starting point to response to the demand for a new monitoring program in the touristic area of Baia di Levante at Vulcano Island (Aeolian archipelago, Italy). Three multiparametric geochemical surveys were carried in the touristic area of Baia di Levante at Vulcano Island (Aeolian archipelago, Italy) in 2011, 2014, and 2015. Carbon dioxide (CO2) and hydrogen sulfide (H2S) are the main undesired components, usually present at the local scale. Anomalous CO2 and H2S outputs from soil and submarine bubbling vents were identified; the thermal anomaly of the ground was mapped; atmospheric concentrations of CO2 and H2S were measured in the air 30 cm above the ground surface. Atmospheric concentrations above the suggested limits for the wellbeing of human health were retrieved in open areas where tourists stay and where CO2 can accumulate under absence of wind.

Highlights

The results of this study focus on minor space and time changes, in the activity state of an active volcanic system, that have been highlighted by repeated multiparameter surveys on the same area
Those space and time changes can foster severe gas hazard conditions in the close proximity of degassing vents, leading to significant risk levels if these features are located inside crowded areas
The increase of hydrothermal volatile release to the atmosphere, evaluated at Baia di Levante (Vulcano Island) in 2015, during a phase of passive degassing, showed that critical concentrations of gases are achieved in open air, with possible harmful effects to human health

Summary

Introduction

The passive release of fluids from hydrothermal and magmatic sources marks the intereruptive periods of a volcanic system. Fluid permeability distribution, ruled by regional tectonic and/or caldera ring faults, controls the pathway toward the surface for magmas and hydrothermal fluids. Its changes have important implications in terms of mineralization, geothermal exploration, and the assessment of volcanic hazard [1,2,3,4,5,6,7]. The soil degassing activity can generate gas hazard, asphyxiation, or poisoning in depressed areas, allowing the accumulation of harmful gases, especially under low wind conditions [8,9]

Methods

Results

Conclusion