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

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.