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@ARTICLE{Tan:857600,
author = {Tan, Zhaofeng and Lu, Keding and Hofzumahaus, Andreas and
Fuchs, Hendrik and Bohn, Birger and Holland, Frank and Liu,
Yuhan and Rohrer, Franz and Shao, Min and Sun, Kang and Wu,
Yusheng and Zeng, Limin and Zhang, Yinsong and Zou, Qi and
Kiendler-Scharr, Astrid and Wahner, Andreas and Zhang,
Yuanhang},
title = {{E}xperimental budgets of {OH}, ${HO}\<sub\>2\</sub\>$ and
${RO}\<sub\>2\</sub\>$ radicals and implications for ozone
formation in the {P}earl {R}iver {D}elta in {C}hina 2014},
journal = {Atmospheric chemistry and physics / Discussions Discussions
[...]},
volume = {acp-2018-801},
issn = {1680-7375},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2018-06585},
pages = {1 - 28},
year = {2018},
abstract = {Hydroxyl (OH) and peroxy radicals (HO2, RO2) were measured
in the Pearl River Delta which is one of the most polluted
areas in China, in autumn 2014. The radical observations
were complemented by measurements of OH reactivity (inverse
OH lifetime) and a comprehensive set of trace gases
including CO, NOx and VOCs. OH reactivity was in the range
between 15s−1 and 80s−1, of which about $50\%$ was
unexplained by the measured OH reactants. In the three weeks
of the campaign, maximum median radical concentrations were
4.5×106cm−3 for OH at noon, and 3×108cm−3 and
2.0×108cm−3 for HO2 and RO2, respectively, in the early
afternoon. The completeness of the daytime radical
measurements made it possible to carry out experimental
budget analyses for all radicals (OH, HO2, and RO2) and
their sum (ROx). The maximum loss rates for OH, HO2, and RO2
reached values between 10ppbv/h and 15ppbv/h during daytime.
The largest fraction of this can be attributed to radical
interconveresio reactions while the real loss rate of ROx
remained below 3ppbv/h. Within experimental uncertainties,
the destruction rates of HO2 and the sum of OH, HO2, and RO2
are balanced by their respective production rates. In case
of RO2, the budget can only be closed when the missing OH
reactivity is attributed to unmeasured VOCs. Thus, the
existence of unmeasured VOCs is directly confirmed by RO2
measurements. Although the closure of the RO2 budget is
greatly improved by the additional unmeasured VOCs, a
significant imbalance in the afternoon remains indicating a
missing RO2 sink. In case of OH, the destruction in the
morning is compensated by the quantified OH sources from
photolysis (HONO, O3), ozonolysis of alkenes and OH
recycling (HO2+NO). In the afternoon, however, the OH budget
indicates a missing OH source of (4–6)ppbv/h. The diurnal
variation of the missing OH source shows a similar pattern
as that of the missing RO2 sink so that both largely
compensate each other in the ROx budget. These observations
suggest the existence of a chemical mechanism that converts
RO2 to OH without the involvement of NO. The photochemical
net ozone production rate calculated from the reaction of
HO2 and RO2 with NO yields a daily integrated amount of
102ppbv ozone with daily integrated ROx primary sources
being 22ppbv in this campaign. This value can be attributed
to the oxidation of measured $(18\%)$ and unmeasured
$(60\%)$ hydrocarbons, formaldehyde $(14\%)$ and CO $(8\%).$
An even larger integrated net ozone production of 140ppbv
would be calculated from the oxidation rate of VOCs with OH,
if HO2 and all RO2 radicals would react with NO. However,
the unknown RO2 loss (evident in the RO2 budget) causes
$30\%$ less ozone production than would be expected from the
VOC oxidation rate.},
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},
doi = {10.5194/acp-2018-801},
url = {https://juser.fz-juelich.de/record/857600},
}