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@ARTICLE{Fuchs:155053,
author = {Fuchs, H. and Acir, I.-H. and Bohn, B. and Brauers, T. and
Dorn, H.-P. and Häseler, R. and Hofzumahaus, A. and
Holland, F. and Kaminski, M. and Li, Xin and Lu, K. and
Lutz, A. and Nehr, S. and Rohrer, F. and Tillmann, R. and
Wegener, R. and Wahner, A.},
title = {{OH} regeneration from methacrolein oxidation investigated
in the atmosphere simulation chamber {SAPHIR}},
journal = {Atmospheric chemistry and physics},
volume = {14},
number = {15},
issn = {1680-7324},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2014-04244},
pages = {7895 - 7908},
year = {2014},
abstract = {Hydroxyl radicals (OH) are the most important reagent for
the oxidation of trace gases in the atmosphere. OH
concentrations measured during recent field campaigns in
isoprene-rich environments were unexpectedly large. A number
of studies showed that unimolecular reactions of organic
peroxy radicals (RO2) formed in the initial reaction step of
isoprene with OH play an important role for the OH budget in
the atmosphere at low mixing ratios of nitrogen monoxide
(NO) of less than 100 pptv. It has also been suggested that
similar reactions potentially play an important role for RO2
from other compounds. Here, we investigate the oxidation of
methacrolein (MACR), one major oxidation product of
isoprene, by OH in experiments in the simulation chamber
SAPHIR under controlled atmospheric conditions. The
experiments show that measured OH concentrations are
approximately $50\%$ larger than calculated by the Master
Chemical Mechanism (MCM) for conditions of the experiments
(NO mixing ratio of 90 pptv). The analysis of the OH budget
reveals an OH source that is not accounted for in MCM, which
is correlated with the production rate of RO2 radicals from
MACR. In order to balance the measured OH destruction rate,
0.77 OH radicals (1σ error: ± 0.31) need to be
additionally reformed from each reaction of OH with MACR.
The strong correlation of the missing OH source with the
production of RO2 radicals is consistent with the concept of
OH formation from unimolecular isomerization and
decomposition reactions of RO2. The comparison of
observations with model calculations gives a lower limit of
0.03 s−1 for the reaction rate constant if the OH source
is attributed to an isomerization reaction of MACR-1-OH-2-OO
and MACR-2-OH-2-OO formed in the MACR + OH reaction as
suggested in the literature (Crounse et al., 2012). This
fast isomerization reaction would be a competitor to the
reaction of this RO2 species with a minimum of 150 pptv NO.
The isomerization reaction would be the dominant reaction
pathway for this specific RO2 radical in forested regions,
where NO mixing ratios are typically much smaller.},
cin = {IEK-8},
ddc = {550},
cid = {I:(DE-Juel1)IEK-8-20101013},
pnm = {233 - Trace gas and aerosol processes in the troposphere
(POF2-233) / HITEC - Helmholtz Interdisciplinary Doctoral
Training in Energy and Climate Research (HITEC)
(HITEC-20170406)},
pid = {G:(DE-HGF)POF2-233 / G:(DE-Juel1)HITEC-20170406},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000341103600016},
doi = {10.5194/acp-14-7895-2014},
url = {https://juser.fz-juelich.de/record/155053},
}