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| Titel |
Characterisation of NO production and consumption: new insights by an improved laboratory dynamic chamber technique |
| VerfasserIn |
T. Behrendt, P. R. Veres, F. Ashuri, G. Song, M. Flanz, B. Mamtimin, M. Bruse, J. Williams, F. X. Meixner |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 19 ; Nr. 11, no. 19 (2014-10-08), S.5463-5492 |
| Datensatznummer |
250117629
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| Publikation (Nr.) |
 copernicus.org/bg-11-5463-2014.pdf |
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| Zusammenfassung |
Biogenic NOx emissions from natural and anthropogenically
influenced soils are currently estimated to amount to 9 Tg a−1, hence
a significant fraction of global NOx emissions
(45 Tg a−1). During the last three decades, a large number of field
measurements have been performed to quantify biogenic NO emissions. To study
biogenic NO emissions as a function of soil moisture, soil temperature, and
soil nutrients, several laboratory approaches have been developed to estimate
local/regional NO emissions by suitable upscaling. This study presents an
improved and automated laboratory dynamic chamber system (consisting of six
individual soil chambers) for investigation and quantification of all
quantities necessary to characterise biogenic NO release from soil (i.e. net
NO release rate, NO production and consumption rate, and respective
Q10 values). In contrast to former versions of the laboratory dynamic
chamber system, the four experiments for complete characterisation can now be
performed on a single soil sample, whereas former studies had to be performed
on four sub-samples. This study discovered that the sub-sample variability
biased former measurements of net NO release rates tremendously. Furthermore,
it was also shown that the previously reported variation of optimum soil
moisture (i.e. where a maximum net NO release rates occur) between
individual sub-samples is most likely a methodical artefact of former
versions of the laboratory dynamic chamber system.
A comprehensive and detailed methodical concept description
of the improved laboratory dynamic chamber system is provided. Response of
all quantities (necessary to characterise net NO release) to soil temperature
and NO mixing ratio of the flushing airstream are determined by automatic
monitoring of these variables during one single drying-out experiment with
one single soil sample only. The method requires precise measurements of NO
mixing ratio at the inlet and outlet of each soil chamber; finally, four
pairs of inlet/outlet NO mixing ratios are sufficient to derive all necessary
quantities. Soil samples from drylands exhibit particularly low NO
production, but even lower NO consumption rates. However, with the improved
laboratory dynamic chamber system those low levels can be quantified, as well
as corresponding NO compensation point mixing ratios and respective
Q10 values. It could be shown that the NO compensation point mixing
ratio seems to be generally independent of gravimetric soil moisture content,
but, particularly for dryland soils, strongly dependent on soil temperature.
New facilities have been included into the improved system (e.g. for
investigation of net release rates of other trace gases, namely CO2 and
volatile
organic compounds – VOCs). First, results are shown for net release rates of acetone
(C3H6O), acetaldehyde (C2H4O) and CO2. This new
system is thus able to simultaneously investigate potential mechanistic links
between NO, multitudinous VOC and CO2. |
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