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| Titel |
Groundwater N2O emission factors of nitrate-contaminated aquifers as derived from denitrification progress and N2O accumulation |
| VerfasserIn |
D. Weymann, R. Well, H. Flessa, C. Heide, M. Deurer, K. Meyer, C. Konrad, W. Walther |
| 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 ; 5, no. 5 ; Nr. 5, no. 5 (2008-09-02), S.1215-1226 |
| Datensatznummer |
250002821
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| Publikation (Nr.) |
 copernicus.org/bg-5-1215-2008.pdf |
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| Zusammenfassung |
| We investigated the dynamics of denitrification and nitrous oxide
(N2O) accumulation in 4 nitrate (NO−3)
contaminated denitrifying sand and gravel aquifers of northern Germany
(Fuhrberg, Sulingen, Thülsfelde and Göttingen) to quantify their
potential N2O emission and to evaluate existing concepts of
N2O emission factors. Excess N2 – N2 produced by denitrification – was determined by using the argon
(Ar) concentration in groundwater as a natural inert tracer, assuming that
this noble gas functions as a stable component and does not change during
denitrification. Furthermore, initial NO−3 concentrations
(NO−3 that enters the groundwater) were derived from
excess N2 and actual NO−3 concentrations in
groundwater in order to determine potential indirect N2O
emissions as a function of the N input. Median concentrations of
N2O and excess N2 ranged from 3 to 89 μg N L−1
and from 3 to 10 mg N L−1, respectively.
Reaction progress (RP) of denitrification was determined as the ratio
between products (N2O-N + excess N2) and
starting material (initial NO−3 concentration) of the
process, characterizing the different stages of denitrification.
N2O concentrations were lowest at RP close to 0 and RP close
to 1 but relatively high at a RP between 0.2 and 0.6. For the first time, we
report groundwater N2O emission factors consisting of the
ratio between N2O-N and initial NO−3-N
concentrations (EF1). In addition, we determined a groundwater emission
factor (EF2) using a previous concept consisting of the ratio
between N2O-N and actual NO−3-N
concentrations. Depending on RP, EF(1) resulted in smaller values
compared to EF(2), demonstrating (i) the relevance of
NO−3 consumption and consequently (ii) the need
to take initial NO−3-N concentrations into account. In
general, both evaluated emission factors were highly variable within and
among the aquifers. The site medians ranged between 0.00043–0.00438 for
EF(1) and 0.00092–0.01801 for EF(2), respectively. For the aquifers of
Fuhrberg and Sulingen, we found EF(1) median values which are close to the
2006 IPCC default value of 0.0025. In contrast, we determined significant
lower EF values for the aquifers of Thülsfelde and Göttingen.
Summing the results up, our study supports the substantial downward
revision of the IPCC default EF5-g from 0.015 (1997) to 0.0025 (2006). |
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