Gas-aerosol chemistry from the hot magma-atmospheric interface to the cooled plume – HalloVolcano

This 3 year project investigates the oxidation chemistry of near-source volcanic plumes by combining a novel model of the chemical processing from the emitted hot magmatic gases to the cooled plume, with drone-based observations of size-resolved aerosols and gases in volcanic plumes (sulfur, halogens mercury), and remote sensing observations of BrO/SO2. We focus on Mt Etna continuous degassing and contrasting Vulcano fumaroles. Hallovolcano will thereby characterize near-source chemistry of volcanic plumes, with a special emphasis on ‘H’ for Halogens and HOx, alongside sulfur. Models suggest that large amounts of HOx are formed by unusual high-temperature chemistry near to the volcano vent that activates halogen radicals within seconds and can form sulfate precursors leading to ‘at-source’ sulfate aerosols. Halogens are emitted as HCl, HBr but are converted into reactive halogens such as BrO through reactions on aerosols, leading to depletion of tropospheric ozone downwind from the volcano. Sulfur, emitted mainly as SO2, competes with the halogens for oxidants, thereby slowing the formation of secondary sulfate aerosols in the downwind plume. Thus, the near-vent and near-downwind processes impact volcanic plume chemistry and aerosol processing on larger scales as the emissions are transported and disperse, as will be traced by incorporating our parameterised halogen chemistry mechanism into a regional-scale model study of volcanic aerosol impacts in the troposphere.