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| Titel |
Measurements of OH and RO2 radicals at Dome C, East Antarctica |
| VerfasserIn |
A. Kukui, M. Legrand, S. Preunkert, M. M. Frey, R. Loisil, J. Gil Roca, B. Jourdain, M. D. King, J. L. France, G. Ancellet |
| 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 ; 14, no. 22 ; Nr. 14, no. 22 (2014-11-26), S.12373-12392 |
| Datensatznummer |
250119185
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| Publikation (Nr.) |
 copernicus.org/acp-14-12373-2014.pdf |
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| Zusammenfassung |
| Concentrations of OH radicals and the sum of peroxy radicals, RO2, were
measured in the boundary layer for the first time on the East Antarctic
Plateau at the Concordia Station (Dome C, 75.10° S,
123.31° E) during the austral summer 2011/2012. The median
concentrations of OH and RO2 radicals were
3.1 × 106 molecule cm−3 and
9.9 × 106 molecule cm−3, respectively. These values are
comparable to those observed at the South Pole, confirming that the elevated
oxidative capacity of the Antarctic atmospheric boundary layer found at the
South Pole is not restricted to the South Pole but common over the high
Antarctic plateau. At Concordia, the concentration of radicals showed
distinct diurnal profiles with the median maximum of
5.2 × 106 molecule cm−3 at 11:00 and the median minimum of
1.1 × 106 molecule cm−3 at 01:00 for OH radicals and
1.7 × 108 molecule cm−3 and
2.5 × 107 molecule cm−3 for RO2 radicals at 13:00 and
23:00, respectively (all times are local times). Concurrent measurements of
O3, HONO, NO, NO2, HCHO and H2O2 demonstrated that the major
primary source of OH and RO2 radicals at Dome C was the photolysis of
HONO, HCHO and H2O2, with the photolysis of HONO contributing
~75% of total primary radical production. However, photochemical
modelling with accounting for all these radical sources overestimates the
concentrations of OH and RO2 radicals by a factor of 2 compared to field
observations. Neglecting the net OH production from HONO in the photochemical
modelling results in an underestimation of the concentrations of OH and
RO2 radicals by a factor of 2. To explain the observations of radicals in
this case an additional source of OH equivalent to about (25–35)% of
measured photolysis of HONO is required. Even with a factor of 5 reduction in
the concentrations of HONO, the photolysis of HONO represents the major
primary radical source at Dome C. To account for a possibility of an
overestimation of NO2 observed at Dome C the calculations were also
performed with NO2 concentrations estimated by assuming steady-state
NO2 / NO ratios. In this case the net radical production from the
photolysis of HONO should be reduced by a factor of 5 or completely removed
based on the photochemical budget of OH or 0-D modelling, respectively.
Another major factor leading to the large concentration of OH radicals
measured at Dome C was large concentrations of NO molecules and fast
recycling of peroxy radicals to OH radicals. |
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