Hydroxyl radical concentrations in isoprene-rich areas have recently been found to be much higher than predicted by existing chemical models; this has consequences for the oxidizing capacity of the global atmosphere. The Leuven Isoprene Mechanism (2009, 2010) aims to explain the OH regeneration in isoprene oxidation at low/moderate NO by novel, theoretically characterized chemical pathways. The key feature of LIM is the isomerisation of specific isoprene-peroxy isomers to yield new classes of compounds and radicals that result in ample OH regeneration. A first such predicted route, through the photolabile HPALDs, has recently found experimental support. Newly characterized parallel routes following peroxy isomerisation, which likewise recycle OH, and reactions of products from new routes converting HO2 into OH, will also be discussed. Model predictions of the combined effects on OH levels, as well as the impact of the new chemistry on SOA formation, will be presented.

Hydroxyl radical regeneration in isoprene oxidation: The Leuven isoprene mechanism

244th National Meeting (2012)

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