Halogen Chemistry in Volcanic Plumes (Invited) - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Communication Dans Un Congrès Année : 2017

Halogen Chemistry in Volcanic Plumes (Invited)

Christof Weber
  • Fonction : Auteur
Helmut Lammer
  • Fonction : Auteur
Ildar F. Shaikhislamov
  • Fonction : Auteur
Nikolai Erkaev
  • Fonction : Auteur
Joshua M. Chadney
  • Fonction : Auteur
Maxim L. Khodachenko
  • Fonction : Auteur
Helmut O. Rucker
  • Fonction : Auteur
Christian Vocks
  • Fonction : Auteur
Wolfgang Macher
  • Fonction : Auteur
Petra Odert
  • Fonction : Auteur
Kristina G. Kislyakova
  • Fonction : Auteur

Résumé

Volcanoes release vast amounts of gases and particles in the atmosphere. Volcanic halogens (HF, HCl, HBr, HI) are co-emitted alongside SO2, and observations show rapid formation of BrO and OClO in the plume as it disperses into the troposphere. The development of 1D and Box models (e.g. PlumeChem) that simulate volcanic plume halogen chemistry aims to characterise how volcanic reactive halogens form and quantify their atmospheric impacts. Following recent advances, these models can broadly reproduce the observed downwind BrO/SO2 ratios using "bromine-explosion" chemistry schemes, provided they use a "high-temperature initialisation" to inject radicals (OH, Cl, Br and possibly NOx) which "kick-start" the low-temperature chemistry cycles that convert HBr into reactive bromine (initially as Br2). The modelled rise in BrO/SO2 and subsequent plateau/decline as the plume disperses downwind reflects cycling between reactive bromine, particularly Br-BrO, and BrO-HOBr-BrONO2. BrCl is produced when aerosol becomes HBr-depleted. Recent model simulations suggest this mechanism for reactive chlorine formation can broadly account for OClO/SO2 reported at Mt Etna. Predicted impacts of volcanic reactive halogen chemistry include the formation of HNO3 from NOx and depletion of ozone. This concurs with HNO3 widely reported in volcanic plumes (although the source of NOx remains under question), as well as observations of ozone depletion reported in plumes from several volcanoes (Mt Redoubt, Mt Etna, Eyjafjallajokull). The plume chemistry can transform mercury into more easily deposited and potentially toxic forms, for which observations are limited. Recent incorporation of volcanic halogen chemistry in a 3D regional model of degassing from Ambrym (Vanuatu) also predicts how halogen chemistry causes depletion of OH to lengthen the SO2 lifetime, and highlights the potential for halogen transport from the troposphere to the stratosphere. However, the model parameter-space is vast and only partially constrained by available observations. Reactions on aerosol are a key driver of the chemistry and are affected by uncertainties in both the HOBr reactive uptake coefficient and the aerosol surface area. Recent work has explored the reactive uptake of HOBr on sulfate-rich aerosol, whilst field-measurements at Mt Etna have aimed to quantify the size-resolved primary aerosol emission, towards improving model representations of this highly non-linear volcanic plume halogen chemistry.
Fichier principal
Vignette du fichier
EGU2017-5061.pdf (42.11 Ko) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte

Dates et versions

insu-03568150 , version 1 (13-02-2022)

Licence

Paternité

Identifiants

Citer

Christof Weber, Helmut Lammer, Ildar F. Shaikhislamov, Nikolai Erkaev, Joshua M. Chadney, et al.. Halogen Chemistry in Volcanic Plumes (Invited). 19th EGU General Assembly, Apr 2017, Vienne, Austria. pp.7578. ⟨insu-03568150⟩
77 Consultations
5 Téléchargements

Partager

Gmail Facebook X LinkedIn More