Reactive halogens in the polar boundary layer and volcanic plumes - Implications for O3, CH4 and mercury

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• Prof Roland von Glasow (UEA)
• Monday 17 February 2014, 14:15-15:30
• Unilever Lecture Theatre, Department of Chemistry.

If you have a question about this talk, please contact Dr Amanda Maycock.

Ozone Depletion Events (ODEs) have been known to occur in the polar boundary layer for over 20 years. During such events, ozone concentrations can fall from background amounts to below instrumental detection limits within a few minutes and remain suppressed for on the order of hours to days. The chemical destruction of ozone is driven by halogens (especially bromine radicals) that have a source associated with the sea ice zone. Although our knowledge of ODEs has increased greatly since their discovery, some of the key processes involved are not yet fully understood.

Despite our increasing understanding of the spatial variability of BrO and possible reaction pathways based on laboratory studies, important questions remain regarding the most efficient sources of and mechanisms for Arctic halogen activation. Recent findings indicate that atmospherically processed snow is likely a major source of Arctic bromine release, which impacts the distribution and occurrence of ozone depletion events and BrO. The implications of snowpack photochemical bromine production on tropospheric reactive bromine concentrations are explored using the one-dimensional halogen model MISTRA -Snow (Thomas et al., 2011, 2012). Further ongoing and planned work will be presented.

Another part of the atmosphere in which halogen chemistry has been found to be of importance in the troposphere is a completely different environment – volcanic plumes. I will present results from recent measurements at the crater rim of Mt Etna as well as numerical simulations from a 1D model and a regional 3D model. These models are used to improve our understanding of the chemical and physical processes within volcanic plumes and to be able to assess the importance of this chemistry for the chemistry of the troposphere.

This talk is part of the Centre for Atmospheric Science seminars, Chemistry Dept. series.

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