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| Titel |
TRANC – a novel fast-response converter to measure total reactive atmospheric nitrogen |
| VerfasserIn |
O. Marx, C. Brümmer, C. Ammann, V. Wolff, A. Freibauer |
| 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 ; 5, no. 5 ; Nr. 5, no. 5 (2012-05-11), S.1045-1057 |
| Datensatznummer |
250002864
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| Publikation (Nr.) |
 copernicus.org/amt-5-1045-2012.pdf |
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| Zusammenfassung |
| The input and loss of plant available nitrogen (reactive nitrogen: Nr)
from/to the atmosphere can be an important factor for the productivity of
ecosystems and thus for its carbon and greenhouse gas exchange. We present a
novel converter for reactive nitrogen (TRANC: Total
Reactive Atmospheric Nitrogen Converter), which offers the opportunity to quantify the sum of all
airborne reactive nitrogen compounds (∑Nr) in high time
resolution. The basic concept of the TRANC is the full conversion of all
Nr to nitrogen monoxide (NO) within two reaction steps. Initially,
reduced Nr compounds are being oxidised, and oxidised Nr compounds
are thermally converted to lower oxidation states. Particulate Nr is
being sublimated and oxidised or reduced afterwards. In a second step,
remaining higher nitrogen oxides or those generated in the first step are
catalytically converted to NO with carbon monoxide used as reduction gas.
The converter is combined with a fast response chemiluminescence detector
(CLD) for NO analysis and its performance was tested for the most relevant
gaseous and particulate Nr species under both laboratory and field
conditions. Recovery rates during laboratory tests for NH3 and NO2
were found to be 95 and 99%, respectively, and 97% when the two
gases were combined. In-field longterm stability over an 11-month period was
approved by a value of 91% for NO2. Effective conversion was also
found for ammonium and nitrate containing particles. The recovery rate of
total ambient Nr was tested against the sum of individual measurements
of NH3, HNO3, HONO, NH4+, NO3−, and NOx
using a combination of different well-established devices. The results show
that the TRANC-CLD system precisely captures fluctuations in ∑Nr
concentrations and also matches the sum of all individual Nr compounds
measured by the different single techniques. The TRANC features a specific
design with very short distance between the sample air inlet and the place
where the thermal and catalytic conversions to NO occur. This assures a
short residence time of the sample air inside the instrument, and minimises
wall sorption problems of water soluble compounds. The fast response time
(e-folding times of 0.30 to 0.35 s were found during concentration step
changes) and high accuracy in capturing the dominant Nr species enables
the converter to be used in an eddy covariance setup. Although a source
attribution of specific Nr compounds is not possible, the TRANC is a
new reliable tool for permanent measurements of the net ∑Nr flux
between ecosystem and atmosphere at a relatively low maintenance and
reasonable cost level allowing for diurnal, seasonal and annual
investigations. |
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