 |
| Titel |
HOx regeneration in isoprene oxidation: evidence for new unimolecular peroxy radical reactions with strong implications for tropospheric chemistry |
| VerfasserIn |
Jozef Peeters, Thanh Lam Nguyen, Luc Vereecken, Jean-Francois Müller |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250033600
|
|
|
|
|
|
| Zusammenfassung |
| HOx re-generation in the oxidation of isoprene, with its global emissions of about 500 Tg/yr,
has a large impact on the global oxidizing capacity of the atmosphere. Recently, we proposed
and theoretically quantified new pathways for the OH-initiated oxidation of isoprene that
might explain the much higher than observed OH concentrations in isoprene-rich
environments (Peeters et al., Phys.Chem.Chem.Phys., 11, 5935, 2009). The new reaction
mechanisms put forward and characterized using high-level theoretical methods include
(i) the very fast interconversion (by O2 elimination and addition) of the various
conformers/isomers of the major isoprene peroxy radicals, (ii) the 1,5-H shift of the major
β-OH-peroxys generating OH with coproducts MACR or MACR, and most importantly, (iii)
the 1,6-H shift of specific conformers (Z-δ-OH-peroxys) followed by reaction with O2
generating HO2 and very photolabile hydroperoxy aldehydes (denoted HPALDs), and
(iv) fast photolysis (with quantum yield approaching unity) as the main sink of
the HPALDs, generating OH and a radical which will give rise to additional OH
formation.
In this communication we present evidence, from recent experimental observations, for the
newly proposed chemistry. The yields of the main first-generation products (HOx,
HPALD, MVK, MACR, but also the hydroxy-aldehydes HALD) will be examined as a
function of NO. The implications regarding the role of isoprene in the atmosphere
will be also briefly discussed. A global modelling study aiming at quantifying the
impact of the new chemistry will be presented in a companion paper in this session. |
|
|
|
|
|
|