Probabilistic hazard modelling of the natural gas emission of Mefite d’Ansanto, Southern Italy

Abstract

The emission of gas species dangerous for human health and life is a widespread source of hazard in various natural contexts. These mainly include volcanic areas but also non-volcanic geological contexts. A notable example of the latter occurrence is the Mefite d’Ansanto area in the Southern Apennines in Italy. Here, significant emissions of carbon dioxide (CO2) occur at rates that make this the largest non-volcanic CO2 gas emission in Italy and probably of the Earth. Given the morphology of the area, in certain meteorological conditions a cold gas stream forms in the valleys surrounding the emission zone, which proved to be potentially lethal for humans and animals in the past. In this study we present a gas hazard modelling study that considers the main specie, that is CO2, and the potential effect of the most dangerous, which is hydrogen sulphide (H2S). For these purposes we used VIGIL, a tool that manages the workflow of gas dispersion simulations specifically optimised for probabilistic hazard applications. We produced maps of CO2 and H2S concentration and persistence at various exceedance probabilities considering the gas emission rates and their possible range of variation defined in previous studies.