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| Titel |
Impacts of an unknown daytime HONO source on the mixing ratio and budget of HONO, and hydroxyl, hydroperoxyl, and organic peroxy radicals, in the coastal regions of China |
| VerfasserIn |
Y. Tang, J. An, F. Wang, Y. Li, Y. Qu, Y. Chen, J. Lin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 16 ; Nr. 15, no. 16 (2015-08-21), S.9381-9398 |
| Datensatznummer |
250119986
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| Publikation (Nr.) |
 copernicus.org/acp-15-9381-2015.pdf |
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| Zusammenfassung |
| Many field experiments have found high nitrous acid (HONO) mixing ratios in
both urban and rural areas during daytime, but these high daytime HONO
mixing ratios cannot be explained well by gas-phase production, HONO
emissions, and nighttime hydrolysis conversion of nitrogen dioxide
(NO2) on aerosols, suggesting that an unknown daytime HONO source
(Punknown) could exist. The formula Punknown ≈ 19.60[NO2] ·
J(NO2) was obtained using observed data from 13 field experiments across
the globe. The three additional HONO sources (i.e., the Punknown,
nighttime hydrolysis conversion of NO2 on aerosols, and HONO emissions)
were coupled into the WRF-Chem model (Weather Research and Forecasting model
coupled with Chemistry) to assess the Punknown impacts on the
concentrations and budgets of HONO and peroxy (hydroxyl, hydroperoxyl, and
organic peroxy) radicals (ROx) (= OH + HO2 + RO2) in
the coastal regions of China. Results indicated that the additional HONO
sources produced a significant improvement in HONO and OH simulations,
particularly in the daytime. High daytime average Punknown values were
found in the coastal regions of China, with a maximum of 2.5 ppb h−1 in
the Beijing–Tianjin–Hebei region. The Punknown produced a
60–250 % increase of OH, HO2, and RO2 near the ground in the
major cities of the coastal regions of China, and a 5–48 % increase
of OH, HO2, and RO2 in the daytime meridional-mean mixing ratios
within 1000 m above the ground. When the three additional HONO sources were
included, the photolysis of HONO was the second most important source in the
OH production rate in Beijing, Shanghai, and Guangzhou before 10:00 LST with
a maximum of 3.72 ppb h−1 and a corresponding Punknown
contribution of 3.06 ppb h−1 in Beijing, whereas the reaction of
HO2 + NO (nitric oxide) was dominant after 10:00 LST with a maximum
of 9.38 ppb h−1 and a corresponding Punknown
contribution of 7.23 ppb h−1 in Beijing. The whole ROx cycle was accelerated by the
three additional HONO sources, especially the Punknown. The daytime
average OH production rate was enhanced by 0.67 due to the three additional
HONO sources; [0.64], due to the Punknown, to 4.32 [3.86] ppb h−1, via
the reaction of HO2 + NO, and by 0.49 [0.47] to 1.86 [1.86] ppb h−1, via the photolysis of HONO. The OH daytime average loss rate
was enhanced by 0.58 [0.55] to 2.03 [1.92] ppb h−1, via the reaction of
OH + NO2, and by 0.31 [0.28] to 1.78 [1.64] ppb h−1, via the
reaction of OH + CO (carbon monoxide) in Beijing, Shanghai, and Guangzhou.
Similarly, the three additional HONO sources produced an increase of 0.31
[0.28] (with a corresponding Punknown contribution) to
1.78 [1.64] ppb h−1, via the reaction of OH + CO, and 0.10 [0.09] to 0.63 [0.59] ppb h−1, via the reaction of CH3O2 (methylperoxy
radical) + NO in the daytime average HO2 production rate, and 0.67 [0.61] to 4.32
[4.27] ppb h−1, via the reaction of HO2 + NO in the daytime
average HO2 loss rate in Beijing, Shanghai, and Guangzhou. The above
results suggest that the Punknown considerably enhanced the ROx
concentrations and accelerated ROx cycles in the coastal regions of
China, and could produce significant increases in concentrations of
inorganic aerosols and secondary organic aerosols and further aggravate haze
events in these regions. |
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