Risk evaluation of SO2 emission at Vulcano island (Sicily)

The island of Vulcano (Aeolian Archipelago, north of Sicily) is site of an intense fumarolic and hydrothermal activity. The main fumaroles, located on the northern ridge of La Fossa crater, emit essentially water vapour, carbon dioxide, sulphurous components and other minor compounds. In particular, SO2 is very dangerous when inhaled (especially when mixed with particles and water vapour). Typical output rates of SO2 in the last few years oscillate in the order of a few tons/day. SO2 concentrations in the air over the island were estimated by numerical codes. Simulations were done using a 3D mesoscale meteorological model for complex terrain. Those were performed for no wind synoptic condition, which is the most significant in terms of hazard. Flow model outputs were then used by a Lagrangian particle model to simulate the dispersion of the gas. Risk scenarios are estimated in the area of Vulcano Porto where, during the summer, more than 10,000 tourists live. The thresholds considered are 200 ppb for provoking asthma in susceptible people (short term effect over minutes), a few ppm for representing a hazard for the normal people, and 400's ppm as an extreme value potentially leading to death.