The influence of isoprene peroxy radical isomeriza

Authors: Haofei Zhang Richard M Kamens

Publish Date: 2012/05/06

Volume: 69, Issue: 1, Pages: 67-81

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Abstract

Isoprene peroxy radical isomerizations 15 and 16H shifts have recently been proposed as important pathways regenerating and recycling HOx OH + HO2 in the atmosphere under lowNOx conditions Peeters et al Phys Chem Chem Phys 28 5935–5939 2009 da Silva et al Environ Sci Technol 44250–256 2010 Evaluation and comparison of the isoprene peroxy radical isomerization mechanisms from recent studies have been performed against isopreneNOx experiments conducted in the UNC dual outdoor smog chambers Five different kinetic mechanisms were tested in this study including the original Master Chemical Mechanism MCM v31 two modified MCM mechanisms both implementing isoprene peroxy radical isomerization reactions but with different rate coefficients the Carbon Bond 6 CB6 mechanism and the ISOUNC mechanism Sensitivity analyses of the unsaturated hydroxyperoxy aldehydes HPALDs reaction mechanisms under fast isomerization have also been performed The results indicate that the fast isomerization mechanism and the mechanisms with high OH yields from HPALDs photolysis both significantly enhance HOx estimates with increasing isoprene/NOx ratios However O3 predictions as well the isoprene decay rates are substantially overestimated Our results suggest that given the current state of our knowledge it is difficult to improve both HOx levels and maintain reasonable O3 simulations using the Peeters et al Peeters et al Phys Chem Chem Phys 28 5935–5939 2009 mechanism

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