| Volumes and Issues Contents of Issue 2 |
www.biogeosciences-discuss.net/5/1263/2008/
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.
Assessment of excess N2 and groundwater N2O emission factors of nitrate-contaminated aquifers in northern Germany
1Soil Science of Temperate and Boreal Ecosystems, Büsgen-Institute, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
2Inst. for Soil Science, Univ. of Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
3HortResearch, Tennent Drive, Palmerston North, 4474 New Zealand
4Geries Ingenieure, Büro für Standorterkundung, Kirchberg 12, 37130 Gleichen, Germany
5Inst. for Groundwater Management, Dresden Univ. of Technology, 01062 Dresden, Germany
Abstract. We investigated the dynamics of denitrification and nitrous oxide (N2O) accumulation in 4 nitrate (NO3−) 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-N2produced 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 NO3− concentrations (NO3− that enters the groundwater) were derived from excess N2 and actual NO3− 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 NO3− 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 NO3−-N concentrations (EF1). According to denitrification intensity, EF(1) was smaller than the ratio between N2O-N and actual NO3−-N concentrations EF(2). In general, these emission factors were highly variable within 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 EFs for the aquifers of Thülsfelde and Göttingen.
Discussion Paper (PDF, 747 KB) Interactive Discussion (Closed, 6 Comments) Final Revised Paper (BG)
Citation: Weymann, D., Well, R., Flessa, H., von der Heide, C., Deurer, M., Meyer, K., Konrad, C., and Walther, W.: Assessment of excess N2 and groundwater N2O emission factors of nitrate-contaminated aquifers in northern Germany, Biogeosciences Discuss., 5, 1263-1292, 2008. Bibtex EndNote Reference Manager
