“Complete depletion” of gaseous elemental mercury observed in the Piton de la Fournaise volcanic plume (April-June 2018 eruption): Proposal of a mercury trapping process by volcanic aerosols

We’ve long known that volcanoes emit mercury, a powerful neurotoxin, into the atmosphere. However, the behavior and transformations of mercury after its emission in a volcanic plume, an extreme and chemically active environment, remain largely unknown. Knowledge of these transformations is of great importance, as they determine whether the emitted mercury compound is transported on a global scale via atmospheric circulation, or deposited locally and regionally at short distances from the emission source. We show, via this study carried out on Reunion Island, using data collected at the Observatoire de Physique Atmosphérique du Maido (OPAR, OSU-R) and around the Piton de la Fournaise volcano during the April-June 2018 eruption, that mercury present in the volcanic plume can be efficiently transformed into rapidly sedimenting chemical compounds that are susceptible to leaching by precipitation. This study implies that terrestrial volcanism can not only emit mercury directly into the atmosphere, as has been previously accepted for many years, but also induce chemical reactions that remove it indirectly and rapidly. Although observation of this process would reduce the mass of mercury emitted and spatially distributed in the atmosphere on a hemispheric or even global scale, the said process would increase mercury deposition and human exposure in active volcanic regions around emission sources.

Reference : Koenig, A., Magand, O., Rose, C., Muro, A., Miyazaki, Y., Colomb, A., Rissanen, M., Lee, C., Koenig, T., Volkamer, R., Brioude, J., Verreyken, B., Roberts, T., Edwards, B., Sellegri, K., Arellano, S., Kowalski, P., Aiuppa, A., Sonke, J., Dommergue, A. (2023). Observed in-plume gaseous elemental mercury depletion suggests significant mercury scavenging by volcanic aerosols. Environmental Science: Atmospheres. 10.1039/D3EA00063J.

Scientific contact OSU-R: Olivier Magand, OSU-R (olivier.magand@cnrs.fr)

Scientific contact IGE: Alkuin Koenig, IGE (alkuin.koenig@univ-grenoble-alpes.fr)

Synthetic diagram of the proposed GEM atmospheric depletion process
(© Alkuin Koenig, IGE)