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Titel |
Measurements of nitrogen oxides and ozone fluxes by eddy covariance at a meadow: evidence for an internal leaf resistance to NO2 |
VerfasserIn |
P. Stella, M. Kortner, C. Ammann, T. Foken, F. X. Meixner, I. Trebs |
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 ; 10, no. 9 ; Nr. 10, no. 9 (2013-09-12), S.5997-6017 |
Datensatznummer |
250085331
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Publikation (Nr.) |
copernicus.org/bg-10-5997-2013.pdf |
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Zusammenfassung |
Nitrogen dioxide (NO2) plays an important role in atmospheric pollution,
in particular for tropospheric ozone production. However, the removal
processes involved in NO2 deposition to terrestrial ecosystems are still
the subject of ongoing discussion. This study reports NO2 flux measurements
made over a meadow using the eddy covariance method. The measured NO2
deposition fluxes during daytime were about a factor of two lower than a
priori calculated fluxes using the Surfatm model without taking into account
an internal (also called mesophyllic or sub-stomatal) resistance. Neither an
underestimation of the measured NO2 deposition flux due to chemical
divergence or an in-canopy NO2 source nor an underestimation of the
resistances used to model the NO2 deposition explained the large
difference between measured and modelled NO2 fluxes. Thus, only the
existence of the internal resistance could account for this large discrepancy
between model and measurements. The median internal resistance was estimated
to be 300 s m−1 during daytime, but exhibited a large variability
(100–800 s m−1). In comparison, the stomatal resistance was only
around 100 s m−1 during daytime. Hence, the internal resistance
accounted for 50–90% of the total leaf resistance to NO2. This
study presents the first clear evidence and quantification of the internal
resistance using the eddy covariance method; i.e. plant functioning was not
affected by changes of microclimatological (turbulent) conditions that
typically occur when using enclosure methods. |
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