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@ARTICLE{Zhao:893415,
author = {Zhao, Defeng and Pullinen, Iida and Fuchs, Hendrik and
Schrade, Stephanie and Wu, Rongrong and Acir, Ismail-Hakki
and Tillmann, Ralf and Rohrer, Franz and Wildt, Jürgen and
Guo, Yindong and Kiendler-Scharr, Astrid and Wahner, Andreas
and Kang, Sungah and Vereecken, Luc and Mentel, Thomas F.},
title = {{H}ighly oxygenated organic molecule ({HOM}) formation in
the isoprene oxidation by ${NO}\<sub\>3\</sub\>$ radical},
journal = {Atmospheric chemistry and physics},
volume = {21},
number = {12},
issn = {1680-7324},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2021-02739},
pages = {9681 - 9704},
year = {2021},
abstract = {Highly oxygenated organic molecules (HOM) are found to play
an important role in the formation and growth of secondary
organic aerosol (SOA). SOA is an important type of aerosol
with significant impact on air quality and climate. Compared
with the oxidation of volatile organic compounds by ozone
(O3) and hydroxyl radical (OH), HOM formation in the
oxidation by nitrate radical (NO3), an important oxidant at
nighttime and dawn, has received less attention. In this
study, HOM formation in the reaction of isoprene with NO3
was investigated in the SAPHIR chamber (Simulation of
Atmospheric PHotochemistry In a large Reaction chamber). A
large number of HOM, including monomers (C5), dimers (C10),
and trimers (C15), both closed-shell compounds and
open-shell peroxy radicals (RO2), were identified and were
classified into various series according to their formula.
Their formation pathways were proposed based on the peroxy
radicals observed and known mechanisms in the literature,
which were further constrained by the time profiles of HOM
after sequential isoprene addition to differentiate first-
and second-generation products. HOM monomers containing one
to three N atoms (1–3N-monomers) were formed, starting
with NO3 addition to carbon double bond, forming peroxy
radicals, followed by autoxidation. 1N-monomers were formed
by both the direct reaction of NO3 with isoprene and of NO3
with first-generation products. 2N-monomers (e.g.,
C5H8N2On(n=7–13), C5H10N2On(n=8–14)) were likely the
termination products of C5H9N2On•, which was formed by the
addition of NO3 to C5-hydroxynitrate (C5H9NO4), a
first-generation product containing one carbon double bond.
2N-monomers, which were second-generation products,
dominated in monomers and accounted for $∼34 \%$ of all
HOM, indicating the important role of second-generation
oxidation in HOM formation in the isoprene + NO3
reaction under our experimental conditions. H shift of
alkoxy radicals to form peroxy radicals and subsequent
autoxidation (“alkoxy–peroxy” pathway) was found to be
an important pathway of HOM formation. HOM dimers were
mostly formed by the accretion reaction of various HOM
monomer RO2 and via the termination reactions of dimer RO2
formed by further reaction of closed-shell dimers with NO3
and possibly by the reaction of C5–RO2 with isoprene. HOM
trimers were likely formed by the accretion reaction of
dimer RO2 with monomer RO2. The concentrations of different
HOM showed distinct time profiles during the reaction, which
was linked to their formation pathway. HOM concentrations
either showed a typical time profile of first-generation
products, second-generation products, or a combination of
both, indicating multiple formation pathways and/or multiple
isomers. Total HOM molar yield was estimated to be
$1.2 \%+1.3\%−0.7\%,$ which corresponded to a SOA yield
of $∼3.6 \%$ assuming the molecular weight of C5H9NO6 as
the lower limit. This yield suggests that HOM may contribute
a significant fraction to SOA yield in the reaction of
isoprene with NO3.},
cin = {IEK-8},
ddc = {550},
cid = {I:(DE-Juel1)IEK-8-20101013},
pnm = {2111 - Air Quality (POF4-211)},
pid = {G:(DE-HGF)POF4-2111},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000668601000003},
doi = {10.5194/acp-21-9681-2021},
url = {https://juser.fz-juelich.de/record/893415},
}