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@ARTICLE{Fuchs:276592,
author = {Fuchs, Hendrik and Tan, Zhaofeng and Hofzumahaus, A. and
Broch, S. and Dorn, H.-P. and Holland, F. and Künstler, C.
and Gomm, Sebastian and Rohrer, F. and Schrade, S. and
Tillmann, R. and Wahner, A.},
title = {{I}nvestigation of potential interferences in the detection
of atmospheric {RO}$_{x}$ radicals by laser-induced
fluorescence under dark conditions},
journal = {Atmospheric measurement techniques discussions},
volume = {8},
number = {11},
issn = {1867-8610},
address = {Katlenburg-Lindau},
publisher = {Copernicus},
reportid = {FZJ-2015-06946},
pages = {12475 - 12523},
year = {2015},
abstract = {Direct detection of highly reactive, atmospheric hydroxyl
radicals (OH) is widely accomplished by laser-induced
fluorescence (LIF) instruments. The technique is also
suitable for the indirect measurement of HO2 and RO2 peroxy
radicals by chemical conversion to OH. It requires sampling
of ambient air into a low pressure cell, where OH
fluorescence is detected after excitation by 308 nm laser
radiation. Although the residence time of air inside the
fluorescence cell is typically only on the order of
milliseconds, there is potential that additional OH is
internally produced, which would artificially increase the
measured OH concentration. Here, we present experimental
studies investigating potential interferences in the
detection of OH and peroxy radicals for the LIF instruments
of Forschungszentrum Jülich for nighttime conditions. For
laboratory experiments, the inlet of the instrument was
overflown by excess synthetic air containing one or more
reactants. In order to distinguish between OH produced by
reactions upstream of the inlet and artificial signals
produced inside the instrument, a chemical titration for OH
was applied. Additional experiments were performed in the
simulation chamber SAPHIR where simultaneous measurements by
an open-path differential optical absorption spectrometer
(DOAS) served as reference for OH to quantify potential
artifacts in the LIF instrument. Experiments included the
investigation of potential interferences related to the
nitrate radical (NO3, N2O5), related to the ozonolysis of
alkenes (ethene, propene, 1-butene, 2,3-dimethyl-2-butene,
α-pinene, limonene, isoprene), and the laser photolysis of
acetone. Experiments studying the laser photolysis of
acetone yield OH signals in the fluorescence cell, which are
equivalent to 0.05 × 106 cm−3 OH for a mixing ratio of 5
ppbv acetone. Under most atmospheric conditions, this
interference is negligible. No significant interferences
were found for atmospheric concentrations of reactants
during ozonolysis experiments. Only for α-pinene, limonene,
and isoprene at reactant concentrations which are orders of
magnitude higher than in the atmosphere artificial OH could
be detected. The value of the interference depends on the
turnover rate of the ozonolysis reaction. For example, an
apparent OH concentration of approximately 1 × 106 cm−3
is observed, if 5.8 ppbv limonene reacts with 600 ppbv
ozone. Experiments with the nitrate radical NO3 reveal a
small interference signal in the OH, HO2 and RO2 detection.
Dependencies on experimental parameters point to artificial
OH formation by surface reactions at the chamber walls or in
molecular clusters in the gas expansion. The signal scales
with the presence of NO3 giving equivalent radical
concentrations of 1.1 × 105 cm−3 OH, 1 × 107 cm−3 HO2,
and 1.7 × 107 cm−3 RO2 per 10 pptv NO3.},
cin = {IEK-8},
ddc = {550},
cid = {I:(DE-Juel1)IEK-8-20101013},
pnm = {243 - Tropospheric trace substances and their
transformation processes (POF3-243) / HITEC - Helmholtz
Interdisciplinary Doctoral Training in Energy and Climate
Research (HITEC) (HITEC-20170406)},
pid = {G:(DE-HGF)POF3-243 / G:(DE-Juel1)HITEC-20170406},
typ = {PUB:(DE-HGF)16},
doi = {10.5194/amtd-8-12475-2015},
url = {https://juser.fz-juelich.de/record/276592},
}