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Published on: June 28, 2019
Total radical yields from tropospheric ethene ozonolysis
Mohammed S Alam1, Marie Camredon, Andrew R Rickard
1School of Geography, Earth & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
Physical Chemistry Chemical Physics : PCCP
|April 14, 2011
Summary
Ethene ozonolysis is a key source of atmospheric radicals. This study quanties radical production and degradation products, yielding specific OH and HO(2) radical yields crucial for atmospheric models.
Area of Science:
- Atmospheric Chemistry
- Chemical Kinetics
Background:
- Gas-phase reactions of ozone with alkenes are significant sources of free radicals (OH, HO(2), and RO(2)) in Earth's atmosphere.
- Ethene ozonolysis is a critical process influencing tropospheric radical budgets.
Purpose of the Study:
- To measure total radical production and degradation products from ethene ozonolysis under tropospheric conditions.
- To determine accurate OH and HO(2) radical yields from ethene ozonolysis.
- To refine atmospheric models by incorporating updated ethene ozonolysis mechanisms.
Main Methods:
- Detailed simulation chamber experiments conducted in the EUPHORE photoreactor.
- Utilized advanced instrumentation including chemical-ionisation-reaction time-of-flight mass-spectrometry (CIR-TOF-MS) and laser-induced fluorescence (LIF).
- Employed OH radical scavengers and chemical chamber box modelling with an updated Master Chemical Mechanism (MCMv3.1).
Main Results:
- Measured the rate coefficient for the ethene + ozone reaction at (1.45 ± 0.25) × 10(-18) cm(3) molecules(-1) s(-1) at 298 K.
- Determined a stabilised Criegee intermediate yield of 0.54 ± 0.12 and an OH radical yield of 0.17 ± 0.09.
- Obtained an averaged HO(2) yield of 0.27 ± 0.07, highlighting the importance of [HO(2)] and scavenger chemistry.
Conclusions:
- The study provides crucial quantitative data on radical yields from ethene ozonolysis.
- Results emphasize the need for accurate knowledge of HO(2) concentrations and scavenger effects in atmospheric radical chemistry.
- Updated mechanism and yields improve the representation of ethene ozonolysis in atmospheric models.
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