Increase of volatiles output in the atmosphere at Vulcano Island inferred by SO2 plume monitoring in the 2021-2022 period.

The volatiles emitted in different way from the active volcanoes have been responsible of the increases of gases in the atmosphere like H2O, SO2, CO2, and H2S.The volatiles are exsolved from the magma batch located below the volcano edifice, during the rising towards the surface interacts with surficial fluids, and come out from the soils, the aquifers, the fumaroles and the main conducts.Near continuous plume SO2 fluxes, measurements have been carried out by a network system of SO2 measurements at Vulcano Island, Italy. Two Scan-DOAS stations belonging to the NOVAC Project are located respectively at NE and SW of volcanic cone. This configuration allowed tracking over 80% of plume emission during the solar year.NOVAC is a permanent network for the measurement of volcanic gas emissions, born in 2005 from a European project to creating and installing automated prototypes capable to monitor gases by volcanic plumes, around the world. The main objective was to quantify global volcanic gas emissions and increase knowledge on changes in volcanic activity by estimating the gases emitted by each individual volcanic system.The fluxes of SO2 plume acquired by the UV-scanning DOAS network showed, in the study period (2021 – 2022), monthly average values between 20 and 121 t d-1. Starting from June 2021 onwards, the SO2 output showed a positive trend with an abrupt increase reaching the highest monthly value in September 2021 (monthly average value= 121 t d-1) and the highest daily measurement 16 November 2021 (daily average = 248 t d-1).The atmospheric dispersion model (AERMOD), designed for simulate the dispersion of air pollutant from stationary anthropogenic and natural emission source, have been utilized to produce the dispersion SO2 maps and evaluate the air SO2 concentrations in the neighboring areas of the Vulcano island. These maps have been constructed using environmental parameters such as wind speed and direction measured by the local network installed in different points of the island and at different altitudes. These SO2 iso-concentration maps compared with the limit values shown in the human health tables have made it possible to identify the most harmful areas.