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

Alkuin M. Koenig; Olivier Magand; Clemence Rose; Andrea Di Muro; Yuzo Miyazaki; Aurelie Colomb; Matti Rissanen; Christopher F. Lee; Theodore K. Koenig; Rainer Volkamer; Jerome Brioude; Bert Verreyken; Tjarda Roberts; Brock A. Edwards; Karine Sellegri; Santiago Arellano; Philippe Kowalski; Alessandro Aiuppa; Jeroen E. Sonke; Aurélien Dommergue

doi:10.1039/D3EA00063J

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

Alkuin M. Koenig,

^a Olivier Magand,

^ab Clemence Rose,^c Andrea Di Muro,^def Yuzo Miyazaki,

^g Aurelie Colomb,^c Matti Rissanen,^hi Christopher F. Lee,

^jk Theodore K. Koenig,^jkl Rainer Volkamer,^jk Jerome Brioude,^m Bert Verreyken,^nopq Tjarda Roberts,^rs Brock A. Edwards,^t Karine Sellegri,^c Santiago Arellano,^u Philippe Kowalski,^de Alessandro Aiuppa,^v Jeroen E. Sonke^w and Aurélien Dommergue^a

Author affiliations

^a Univ. Grenoble Alpes, CNRS, INRAE, IRD, Grenoble INP, IGE, 38000 Grenoble, France

^b Observatoire des Sciences de l'Univers à La Réunion (OSU-R), UAR 3365, CNRS, Université de La Réunion, Météo France, 97744 Saint-Denis, La Réunion, France

^c Université Clermont Auvergne, CNRS, Laboratoire de Météorologie Physique (LaMP), 63000 Clermont-Ferrand, France

^d Observatoire Volcanologique du Piton de la Fournaise, Institut de physique du globe de Paris, La Plaine des Cafres, France

^e Institut de physique du globe de Paris, CNRS, Université de Paris, Paris, France

^f Université Claude Bernard Lyon1, Observatoire de Lyon, Laboratoire LGL-TPE, Lyon, France

^g Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan

^h Aerosol Physics Laboratory, Tampere University, FI-33101 Tampere, Finland

ⁱ Department of Chemistry, University of Helsinki, FI-00014 Helsinki, Finland

^j Department of Chemistry, University of Colorado Boulder, Boulder, CO 80309, USA

^k Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA

^l Key Joint Laboratory of Environmental Simulation and Pollution Control, BIC-ESAT and IJRC, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China

^m Laboratoire de l'Atmosphère et des Cyclones, UMR 8105, CNRS, Université de La Réunion, Météo France, 97744 Saint-Denis, France

ⁿ Royal Belgian Institute for Space Aeronomy, 1180 Brussels, Belgium

^o Department of Chemistry, Ghent University, 9000 Ghent, Belgium

^p Laboratoire de l'Atmosphère et des Cyclones, UMR 8105, CNRS, Université de La Réunion, Météo France, 97744 Saint-Denis, France

^q Biosystems Dynamics and Exchanges (BIODYNE), Gembloux Agro-Biotech, University of Liège, 5030 Gembloux, Belgium

^r LPC2E, Laboratoire de Physique et de Chimie de l'Environnement et de l`Espace, University Orléans, CNRS, Orléans, France

^s LMD/IPSL, ENS, Université PSL, École Polytechnique, Institut Polytechnique de Paris, Sorbonne Université, CNRS, Paris, France

^t Centre for Earth Observation Science, Department of Environment and Geography, University of Manitoba, Winnipeg, Canada

^u Department of Space, Earth and Environment, Chalmers University of Technology, Göteborg, Sweden

^v Dipartimento di Scienze della Terra e del Mare, Università di Palermo, Palermo, Italy

^w Géosciences Environnement Toulouse, CNRS/IRD/Université Paul Sabatier Toulouse 3, Toulouse, France

Abstract

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 (∼3–7 hours) volcanic plumes from Piton de la Fournaise on Réunion 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.

Environmental Science: Atmospheres

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

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

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