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| Titel |
Application of a GC-ECD for measurements of biosphere–atmosphere exchange fluxes of peroxyacetyl nitrate using the relaxed eddy accumulation and gradient method |
| VerfasserIn |
A. Moravek, T. Foken, I. Trebs |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 7 ; Nr. 7, no. 7 (2014-07-10), S.2097-2119 |
| Datensatznummer |
250115846
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| Publikation (Nr.) |
 copernicus.org/amt-7-2097-2014.pdf |
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| Zusammenfassung |
| Peroxyacetyl nitrate (PAN) may constitute a significant fraction of reactive
nitrogen in the atmosphere. Current knowledge about the biosphere–atmosphere
exchange of PAN is limited, and only few studies have investigated the
deposition of PAN to terrestrial ecosystems. We developed a flux measurement
system for the determination of biosphere–atmosphere exchange fluxes of PAN
using both the hyperbolic relaxed eddy accumulation (HREA) method and the
modified Bowen ratio (MBR) method. The system consists of a modified,
commercially available gas chromatograph with electron capture detection
(GC-ECD, Meteorologie Consult GmbH, Germany). Sampling was performed by
trapping PAN onto two pre-concentration columns; during HREA operation one
was used for updraft and one for downdraft events, and during MBR operation
the two columns allowed simultaneous sampling at two measurement heights.
The performance of the PAN flux measurement system was tested at a natural
grassland site, using fast-response ozone (O3) measurements as a proxy
for both methods. The measured PAN fluxes were comparatively small (daytime
PAN deposition was on average −0.07 nmol m−2 s−1) and, thus,
prone to significant uncertainties. A major challenge in the design of the
system was the resolution of the small PAN mixing ratio differences.
Consequently, the study focuses on the performance of the analytical unit
and a detailed analysis of errors contributing to the overall uncertainty.
The error of the PAN mixing ratio differences ranged from 4 to 15 ppt
during
the MBR and between 18 and 26 ppt during the HREA operation, while during
daytime measured PAN mixing ratios were of similar magnitude. Choosing
optimal settings for both the MBR and HREA method, the study shows that the
HREA method did not have a significant advantage towards the MBR method
under well-mixed conditions as was expected. |
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