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Article Dans Une Revue Environmental Science : Atmospheres Année : 2023

Observed in-plume gaseous elemental mercury depletion suggests significant mercury scavenging by volcanic aerosols

Clemence Rose
Yuzo Miyazaki
Matti Rissanen
  • Fonction : Auteur
Christopher F Lee
Theodore K Koenig
  • Fonction : Auteur
Rainer Volkamer
  • Fonction : Auteur
Brock A Edwards
  • Fonction : Auteur
Santiago Arellano
  • Fonction : Auteur
Philippe Kowalski
  • Fonction : Auteur
Alessandro Aiuppa
  • Fonction : Auteur
Jeroen E Sonke

Résumé

Terrestrial volcanism is known to emit mercury (Hg) into the atmosphere. However, despite many years of investigation, its net impact on the atmospheric Hg budget remains insufficiently constrained, in part because the transformations of Hg in volcanic plumes as they age and mix with background air are poorly understood. Here we report the observation of complete gaseous elemental mercury (GEM) depletion events in dilute and moderately aged (& SIM;3-7 hours) volcanic plumes from Piton de la Fournaise on Reunion Island. While it has been suggested that co-emitted bromine could, once photochemically activated, deplete GEM in a volcanic plume, we measured low bromine concentrations in both the gas- and particle-phase and observed complete GEM depletion even before sunrise, ruling out a leading role of bromine chemistry here. Instead, we hypothesize that the GEM depletions were mainly caused by gas-particle interactions with sulfate-rich volcanic particles (mostly of submicron size), abundantly present in the dilute plume. We consider heterogeneous GEM oxidation and GEM uptake by particles as plausible manifestations of such a process and derive empirical rate constants. By extrapolation, we estimate that volcanic aerosols may scavenge 210 Mg y(-1) (67-480 Mg y(-1)) of Hg from the atmosphere globally, acting effectively as atmospheric mercury sink. While this estimate is subject to large uncertainties, it highlights that Hg transformations in aging volcanic plumes must be better understood to determine the net impact of volcanism on the atmospheric Hg budget and Hg deposition pathways.
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Dates et versions

hal-04183241 , version 1 (18-08-2023)

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Paternité

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Alkuin M Koenig, Olivier Magand, Clemence Rose, Andrea Di Muro, Yuzo Miyazaki, et al.. Observed in-plume gaseous elemental mercury depletion suggests significant mercury scavenging by volcanic aerosols. Environmental Science : Atmospheres , 2023, ⟨10.1039/D3EA00063J⟩. ⟨hal-04183241⟩
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