Observed in-plume gaseous elemental mercury depletion suggests significant mercury scavenging by volcanic aerosols
Journal article, 2023
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.
Author
Alkuin M. Koenig
Grenoble Alpes University
Olivier Magand
Université de La Réunion
Grenoble Alpes University
Clemence Rose
Clermont Auvergne University
Andrea Di Muro
Claude Bernard University Lyon 1 (UCBL)
Institut de Physique du Globe de Paris
Paris Descartes University
Yuzo Miyazaki
Hokkaido University
Aurelie Colomb
Clermont Auvergne University
Matti Rissanen
University of Tampere
University of Helsinki
Christopher F. Lee
University of Colorado at Boulder
Theodore K. Koenig
Peking University
University of Colorado at Boulder
Rainer Volkamer
University of Colorado at Boulder
Jerome Brioude
Université de La Réunion
Bert Verreyken
Université de La Réunion
Ghent university
University of Liège
Belgian Institute for Space Aeronomy (BIRA-IASB)
Tjarda Roberts
University of Orléans
Sorbonne University
Brock A. Edwards
University of Manitoba
Karine Sellegri
Clermont Auvergne University
Santiago Arellano
Chalmers, Space, Earth and Environment, Geoscience and Remote Sensing
Philippe Kowalski
Institut de Physique du Globe de Paris
Paris Descartes University
Alessandro Aiuppa
University of Palermo
Jeroen E. Sonke
Paul Sabatier University
Aurelien Dommergue
Grenoble Alpes University
Environmental Science: Atmospheres
26343606 (eISSN)
Vol. 3 10 1418-1438Global Volcanic and Atmospheric Observation Programme
Swedish National Space Board (149/18), 2019-04-01 -- 2023-03-31.
Subject Categories
Subatomic Physics
Meteorology and Atmospheric Sciences
DOI
10.1039/d3ea00063j