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@ARTICLE{Crowley:857862,
author = {Crowley, John N. and Pouvesle, Nicolas and Phillips, Gavin
J. and Axinte, Raoul and Fischer, Horst and Petäjä, Tuukka
and Nölscher, Anke and Williams, Jonathan and Hens,
Korbinian and Harder, Hartwig and Martinez-Harder, Monica
and Novelli, Anna and Kubistin, Dagmar and Bohn, Birger and
Lelieveld, Jos},
title = {{I}nsights into {HO}x and {RO}x chemistry in the boreal
forest via measurement of peroxyacetic acid, peroxyacetic
nitric anhydride ({PAN}) and hydrogen peroxide},
journal = {Atmospheric chemistry and physics},
volume = {18},
number = {18},
issn = {1680-7324},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2018-06825},
pages = {13457 - 13479},
year = {2018},
abstract = {Unlike many oxidised atmospheric trace gases, which have
numerous production pathways, peroxyacetic acid (PAA) and
PAN are formed almost exclusively in gas-phase reactions
involving the hydroperoxy radical (HO2), the acetyl peroxy
radical (CH3C(O)O2) and NO2 and are not believed to be
directly emitted in significant amounts by vegetation. As
the self-reaction of HO2 is the main photochemical route to
hydrogen peroxide (H2O2), simultaneous observation of PAA,
PAN and H2O2 can provide insight into the HO2 budget. We
present an analysis of observations taken during a
summertime campaign in a boreal forest that, in addition to
natural conditions, was temporarily impacted by two
biomass-burning plumes. The observations were analysed using
an expression based on a steady-state assumption using
relative PAA-to-PAN mixing ratios to derive HO2
concentrations. The steady-state approach generated HO2
concentrations that were generally in reasonable agreement
with measurements but sometimes overestimated those observed
by factors of 2 or more. We also used a chemically simple,
constrained box model to analyse the formation and reaction
of radicals that define the observed mixing ratios of PAA
and H2O2. After nudging the simulation towards observations
by adding extra, photochemical sources of HO2 and CH3C(O)O2,
the box model replicated the observations of PAA, H2O2, ROOH
and OH throughout the campaign, including the
biomass-burning-influenced episodes during which
significantly higher levels of many oxidized trace gases
were observed. A dominant fraction of CH3O2 radical
generation was found to arise via reactions of the CH3C(O)O2
radical. The model indicates that organic peroxy radicals
were present at night in high concentrations that sometimes
exceeded those predicted for daytime, and initially
divergent measured and modelled HO2 concentrations and daily
concentration profiles are reconciled when organic peroxy
radicals are detected (as HO2) at an efficiency of $35\%.$
Organic peroxy radicals are found to play an important role
in the recycling of OH radicals subsequent to their loss via
reactions with volatile organic compounds.},
cin = {IEK-8},
ddc = {550},
cid = {I:(DE-Juel1)IEK-8-20101013},
pnm = {243 - Tropospheric trace substances and their
transformation processes (POF3-243)},
pid = {G:(DE-HGF)POF3-243},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000445271300003},
doi = {10.5194/acp-18-13457-2018},
url = {https://juser.fz-juelich.de/record/857862},
}