Volcanic plume gases and particles characterization using sounding balloons: the VOLANDO project

Volcanic eruptions emit large amounts of particles (ash, water droplets) and gases (mostly H2O, CO2, SO2 and HCl) into the atmosphere with severe implications on environment, climate, life on Earth, human society and aviation. If the SO2 retrievals, made by remote sensing systems, is generally considered reliable (errors ranging from 30 to 40%), the presence of ash in the volcanic clouds makes it more uncertain (errors increase being even greater than 100%). Moreover, the estimates of volcanic CO2 is extremely critical due to the large quantity of this gas already present in the atmosphere, while the altitude and thickness of the volcanic cloud is generally challenging to retrieve. Finally, great uncertainty is found on the ash optical properties and size distribution. For all these reasons, in order to obtain a precise characterization of volcanic clouds, a direct sampling of gases and particles at different altitudes is required. In this work we present the preliminary results obtained from field campaign made on Etna volcano in 2024 in the sphere of the VOLANDO (VOlcanic pLume chAracterization using sounNDing balloOns) project funded by the Next Generation EU plan. During the campaign airborne systems, equipped with different instruments for ash and gases measurement and sampling, will be tested. A customized “volcanosonde” sensor package has been designed, manufactured and airlifted by sounding balloons in free-flying and tethered configurations or dropped by a high-altitude balloon from above the volcanic cloud. The volcanosondes include a sensor package for ash (concentration and PSD), gases (H2O, CO2, SO2 and HCl) and atmospheric parameters (pressure and temperature) estimations, telemetry and monitoring system. All the configurations of the “volcanosondes” are planned to provide a profile of the species with a spatial resolution of at least 50 m. The tethered balloon will also provide a high temporal resolution and relatively long-term coverage. The results of the VOLANDO project will provide a comprehensive view of a volcanic cloud inner structure and composition contributing to validate remote sensing retrievals, improve dispersion models and contribute to understand volcanic processes and mitigate the risks on both local population and airspace.