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| Titel |
Sources of Nitrous Acid, Formaldehyde, and Hydroxyl Radical in Doha, Qatar. |
| VerfasserIn |
Luis Ackermann, Bernhard Rappenglueck, Mohammed Ayoub |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250153544
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| Publikation (Nr.) |
 EGU/EGU2017-18540.pdf |
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| Zusammenfassung |
| One of the most important species in the atmosphere is the hydroxyl radical (OH), due to its
role controlling the oxidizing capacity of an air shed. The main formation processes of OH
include the photolysis of ozone (O3), nitrous acid (HONO), formaldehyde (HCHO), and the
ozonolysis of alkenes. Still, the sources of HONO in the atmosphere are not sufficiently well
known, with indications that heterogeneous reactions on surfaces may contribute to the
observed concentrations. The city of Doha in Qatar presents a unique opportunity to explore
photochemical processes including the effects of high particulates concentrations under
extreme weather conditions (high temperatures and humidity) and complex emission
sources.
Two Intensive Observational Periods (IOP) were conducted in Doha in 2016, one during
the winter and the other during the summer. These consisted of meteorological
measurements, ozone (O3), nitrous acid (HONO), formaldehyde (HCHO), nitrogen
monoxide (NO), direct nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide
(CO), as well as particulate matter with an aerodynamic diameter ≤ 10 μm and 2.5 μm
(PM10 and PM2.5). In addition photolysis rates of HONO, HCHO, NO2, and singlet oxygen
(O1D) were measured.
The photostationary state concentration of OH was calculated from its known sources and
sinks. The maximum hourly average concentration of OH was determined to be
around 1.1 ppt for summer and 0.5 ppt for winter IOP. For the 24-hr average, the
photolysis of HONO was the main precursor for OH production with 54.3 % and 72.7 %
(summer and winter IOP), while the photolysis of O3 was responsible for 23.8 % and
19.7 % and the photolysis of HCHO accounted for 21.9 % and 7.6 % (summer and
winter IOP, respectively). In this study we present source apportionment analysis for
the radical precursors HONO and HCHO during the winter and summer IOP and
its diurnal variation and elucidate their impact on OH production. We also infer
NOx vs VOC limitation of O3 production from NO2 and HCHO observations. |
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