High-temperature mixtures of magmatic and atmospheric gases

Journal article

Recent measurements of BrO, NOx, and near-source sulfate in volcanic plumes suggest that volcanic vents might not simply act as point sources of emissions into the troposphere, but may also act as hightemperature reaction sites where mixtures of magmatic and ambient atmospheric gases may combine, giving new and previously unexpected reaction products. The detection of such species demands that a more complex model be developed for the interaction of volcanoes and atmospheres. We show that general thermodynamic models can be applied successfully to volcanic gas equilibria by comparing the results from HSC Chemistry with those from two volcanic gas equilibrium models (Solvgas and Gasmix). Using a thermodynamic model optimized for volcanic gas chemistry (C-O-S-H-F-Cl-Br-I-N-Ar speciation), we show that the volume ratio of atmospheric gas to magmatic gas in a high-temperature mixture is an important parameter of the volcanic plume chemistry, and our results suggest that even small amounts of air (a few % for an H2O-rich magmatic gas) in the high-temperature mixture are sufficient to yield elevated levels of reactive nitrogen, halogen (Cl, Br, and I), and sulfur species within the volcanic plume. Further modifications of the plume chemistry may also occur due to low-temperature reactions, and chemical schemes for the modification of halogen (Cl, Br, I), nitrogen, and sulfur chemistry are suggested, within the constraints imposed by recent measurements. Copyright 2006 by the American Geophysical Union.

Authors: Martin, R; Mather, T; Pyle, D

• Publication status: Published
• Journal: GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
• Volume: 7
• Issue: 4
• Pages: n/a-n/a
• Publication date: 2006-04-13
• DOI: 10.1029/2005GC001186
• EISSN: 1525-2027
• ISSN: 1525-2027
• Language: English
• Keywords: volcanic gases; thermodynamic models; atmospheric chemistry; volcanology : volcanic gases; atmospheric composition and structure : troposphere : composition and chemistry; volcanology : atmospheric effects