title: The origin of stable halogenated compounds in volcanic gases.
abstract: BACKGROUND
  Halogenated compounds in the atmosphere are of great environmental concern due to their demonstrated negative effect on atmospheric chemistry and climate. Detailed knowledge of the emission budgets of halogenated compounds has to be gained to understand better their specific impact on ozone chemistry and the climate. Such data are also highly relevant to guide policy decisions in connexion with international agreements about protection of the ozone layer. In selected cases, the relevance of specific emission sources for certain compounds were unclear. In this study we present new and comprehensive evidence regarding the existence and relevance of a volcanic contribution of chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), halons (bromine containing halo(hydro)carbons), and fully fluorinated compounds (e.g. CF4 and SF6) to the atmospheric budget.
  
  
  METHODS
  In order to obtain new evidence of a volcanic origin of these compounds, we collected repeatedly, during four field campaigns covering a period of two years, gases from fumaroles discharging over a wide range of temperatures at the Nicaraguan subduction zone volcanoes Momotombo, Cerro Negro and Mombacho, and analysed them with very sensitive GC/MS systems.
  
  
  CONCLUSIONS
  In most fumarolic samples certain CFCs, HFCs, HCFCs, halons, and the fully fluorinated compounds CF4 and SF6 were present above detection limits. However, these compounds occur in the fumarole gases in relative proportions characteristic for ambient air.
  
  
  CONCLUSIONS
  This atmospheric fingerprint can be explained by variable amounts of air entering the porous volcanic edifices and successively being incorporated into the fumarolic gas discharges. Recommendation and Outlook. Our results suggest that the investigated volcanoes do not constitute a significant natural source for CFCs, HFCs, HCFCs, halons, CF4, SF6 and NF3.
authors.affiliation: SFB 574, Christian-Albrechts-University, 24148 Kiel, Germany. mfrische@ifm-geomar.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Frische
authors.forename: Kristin
authors.initials: K
authors.lastname: Garofalo
authors.forename: Thor H
authors.initials: TH
authors.lastname: Hansteen
authors.forename: Reinhard
authors.initials: R
authors.lastname: Borchers
authors.forename: Jochen
authors.initials: J
authors.lastname: Harnisch
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry*; D001272:Atmosphere / Q000032:analysis / Q000737:chemistry*; D004784:Environmental Monitoring; D008401:Gas Chromatography-Mass Spectrometry; D006846:Hydrocarbons, Halogenated / Q000032:analysis / Q000737:chemistry*; D009527:Nicaragua; D013696:Temperature; D018707:Volcanic Eruptions
chemical_list: D000393:Air Pollutants; D006846:Hydrocarbons, Halogenated