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@ARTICLE{Garmash:902268,
author = {Garmash, Olga and Rissanen, Matti P. and Pullinen, Iida and
Schmitt, Sebastian and Kausiala, Oskari and Tillmann, Ralf
and Zhao, Defeng and Percival, Carl and Bannan, Thomas J.
and Priestley, Michael and Hallquist, Åsa M. and Kleist,
Einhard and Kiendler-Scharr, Astrid and Hallquist, Mattias
and Berndt, Torsten and McFiggans, Gordon and Wildt, Jürgen
and Mentel, Thomas F. and Ehn, Mikael},
title = {{M}ulti-generation {OH} oxidation as a source for highly
oxygenated organic molecules from aromatics},
journal = {Atmospheric chemistry and physics},
volume = {20},
number = {1},
issn = {1680-7324},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2021-04131},
pages = {515 - 537},
year = {2020},
abstract = {Recent studies have recognised highly oxygenated organic
molecules (HOMs) in the atmosphere as important in the
formation of secondary organic aerosol (SOA). A large number
of studies have focused on HOM formation from oxidation of
biogenically emitted monoterpenes. However, HOM formation
from anthropogenic vapours has so far received much less
attention. Previous studies have identified the importance
of aromatic volatile organic compounds (VOCs) for SOA
formation. In this study, we investigated several aromatic
compounds, benzene (C6H6), toluene (C7H8), and naphthalene
(C10H8), for their potential to form HOMs upon reaction with
hydroxyl radicals (OH). We performed flow tube experiments
with all three VOCs and focused in detail on benzene HOM
formation in the Jülich Plant Atmosphere Chamber (JPAC). In
JPAC, we also investigated the response of HOMs to NOx and
seed aerosol. Using a nitrate-based chemical ionisation mass
spectrometer (CI-APi-TOF), we observed the formation of HOMs
in the flow reactor oxidation of benzene from the first OH
attack. However, in the oxidation of toluene and
naphthalene, which were injected at lower concentrations,
multi-generation OH oxidation seemed to impact the HOM
composition. We tested this in more detail for the benzene
system in the JPAC, which allowed for studying longer
residence times. The results showed that the apparent molar
benzene HOM yield under our experimental conditions varied
from $4.1 \%$ to $14.0 \%,$ with a strong dependence on
the OH concentration, indicating that the majority of
observed HOMs formed through multiple OH-oxidation steps.
The composition of the identified HOMs in the mass spectrum
also supported this hypothesis. By injecting only phenol
into the chamber, we found that phenol oxidation cannot be
solely responsible for the observed HOMs in benzene
experiments. When NOx was added to the chamber, HOM
composition changed and many oxygenated nitrogen-containing
products were observed in CI-APi-TOF. Upon seed aerosol
injection, the HOM loss rate was higher than predicted by
irreversible condensation, suggesting that some undetected
oxygenated intermediates also condensed onto seed aerosol,
which is in line with the hypothesis that some of the HOMs
were formed in multi-generation OH oxidation. Based on our
results, we conclude that HOM yield and composition in
aromatic systems strongly depend on OH and VOC concentration
and more studies are needed to fully understand this effect
on the formation of HOMs and, consequently, SOA. We also
suggest that the dependence of HOM yield on chamber
conditions may explain part of the variability in SOA yields
reported in the literature and strongly advise monitoring
HOMs in future SOA studies.},
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:000507330900001},
doi = {10.5194/acp-20-515-2020},
url = {https://juser.fz-juelich.de/record/902268},
}