Estimation of Indirect Nitrous Oxide Emissions from a Shallow Aquifer in Northern Germany
- Carolin von der Heide *a,
- Jürgen Böttchera,
- Markus Deurerb,
- Wilhelmus H.M. Duijnisveldc,
- Daniel Weymannd and
- Reinhard Welle
- a Institute of Soil Science, Univ. of Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
b Plant & Food Research Palmerston North Private Bag 11030, Manawatu Mail Centre, Palmerston North, 4442, New Zealand
c Federal Institute for Geosciences and Natural Resources, Stilleweg 2, 30655 Hannover, Germany
d Institute of Soil Science and Forest Nutrition, Univ. of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
e Johann Heinrich von Thünen-Institut, Federal Research Institute for Rural Areas, Forestry and Fisheries, Institute of Agricultural Climate Research, Bundesallee 50, 38116 Braunschweig, Germany
Ground water is considered to be an important source for indirect N2O emissions. We investigated indirect N2O emissions from a shallow aquifer in Germany over a 1-yr period. Because N2O accumulated in considerable amounts in the surface ground water (mean, 52.86 μg N2O–N L−1) and corresponding fluxes were high (up to 34 μg N2O–N m−2 h−1), it was hypothesized that significant indirect N2O emissions would occur via the vertical and the lateral emission pathway. Vertical N2O emissions were investigated by measuring N2O concentrations and calculating fluxes from the surface ground water to the unsaturated zone and at the soil surface. Lateral N2O fluxes were investigated by measuring ground water N2O and NO3 − concentrations at five multilevel wells and at a waterworks well. Negligible amounts of N2O were emitted vertically into the unsaturated zone; most of it was convectively transported into the deeper autotrophic denitrification zone. Only a ground water level fall and rise triggered the emission of N2O (up to 3 μg N2O–N m−2 h−1) into the unsaturated zone. Ground water–derived N2O was probably reduced during the upward diffusion, and soil surface emissions were governed by topsoil processes. Along the lateral pathway, N2O and NO3 − concentrations decreased with increasing depth in the aquifer. Discharging ground water was almost free of N2O and NO3 −, and indirect N2O emissions were small.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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