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| Titel |
Temperature Dependence of the Rate Constant and Product Studies for BrO with CH3O2 using a Turbulent Flow Tube coupled to Chemical Ionisation Mass Spectrometry |
| VerfasserIn |
K. Leather, A. Bacak, D Shallcross, C. Percival |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058871
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| Zusammenfassung |
| The importance of halogen chemistry in the atmosphere and its contribution to ozone
depletion is widely recognised (Farman et al. 1985; Lary and Toumi, 1997). Bromine plays a
major role in catalytic cycles leading to the destruction of ozone (Salawitch, 2009; Yang,
2005) not only in the stratosphere (Anderson et al., 1991) but also parts of the troposphere, in
particular the marine boundary layer (Saiz-Lopez et al., (2006) as exemplified by the catalytic
cycle below.
Br + O 3 - BrO + O2(1)
BrO + CH3O2 - HOBr + CH2O2(2)
HOBr + hv - Br + OH (3)
OH + CH4 - CH3 + H2O (4)
CH3 + O2 - CH3O2(5)
Net: CH4 + O3 - CH2O2 + H2O (6)
Satellite measurements of BrO have been taken in northern and southern hemispheres
(Simpson et al., 2007 and references therein). Gas-phase kinetic data exist for reaction of XO
(BrO, ClO, IO) with O3, NOx and HOxthough there are limited data concerning the reaction
of XO with CH3O2. In order to improve modelling of halogen related chemical processes
leading to ozone depletion, the determination of reaction rates and product branching
ratios is essential. Since the fates of BrO are not yet fully understood, a turbulent
flow chemical ionisation mass spectrometer (CIMS) shall be employed to study the
kinetics and product yields of the BrO + CH3O2 pathway. Experiments will be
conducted for reaction (2) under pseudo first order conditions using very low radical
concentrations, typically (0.5 – 20) Ã 1010 molecule cm-3. Rate determinations will be
retrieved as a function of atmospherically relevant temperatures (T = 180 – 300
K).
References
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