TY - JOUR

T1 - Spatial and temporal variability of N2O in the surface groundwater

T2 - A detailed analysis from a sandy aquifer in northern Germany

AU - von der Heide, C.

AU - Böttcher, J.

AU - Deurer, M.

AU - Duijnisveld, W. H.M.

AU - Weymann, D.

AU - Well, R.

N1 - Funding information: Acknowledgments We thank H. Flessa, D. Eisermann, H. Geistlinger and K. Schäfer for many helpful discussions. The field and lab work would not have been possible without the help of G. Klump, F. Trienen, M. Wiwiorra, P. Wiese, S. Bokeloh, A. Keitel, I. Ostermeyer and K. Schmidt. Finally we want to thank the German Research Foundation (DFG) for funding this research.

PY - 2010/5

Y1 - 2010/5

N2 - The knowledge of the spatial and temporal variability of N2O concentrations in surface groundwater is the first step towards upscaling of potential indirect N2O emissions from the scale of localized samples to aquifers. This study aimed to investigate the spatial and the temporal variability of N2O concentrations at different scales in the surface groundwater of a denitrifying aquifer in northern Germany. The spatial variability of N2O concentrations in the surface groundwater was analysed at the plot (200 × 200 m) and at the transect scale (12 m). Twenty plots that were distributed across an area of 11 km2 and 6 transects were sampled. Sixty per cent of the spatial variance of N2O was located at the plot scale and 68-79% was located at the transect scale. This indicates that small-scale processes governed the spatial variability of N2O in the surface groundwater. A spatial upscaling of N2O from the transect to the aquifer scale might be possible with an adequate number of samples that represent important boundary conditions for N2O accumulation in the catchment (topography, groundwater level, land use). For the investigation of the temporal variability, 4 multilevel wells were sampled monthly over a period of 13 months. In two periods, a multilevel well was additionally sampled in 2-day intervals over 8 days. At the annual scale, N2O concentrations in the surface groundwater were higher during the vegetation period (median 87 μg N2O-N l-1) and could change rapidly on the day scale whereas the concentrations were smaller in winter (median 21 μg N2O-N l-1). Groundwater recharge events seemed to be crucial for the day scale variability. Capture of the temporal variations for upscaling might be achieved with a process-based sampling strategy with weekly sampling intervals during the vegetation period, the additional sampling after groundwater recharge events and monthly sampling intervals in winter.

AB - The knowledge of the spatial and temporal variability of N2O concentrations in surface groundwater is the first step towards upscaling of potential indirect N2O emissions from the scale of localized samples to aquifers. This study aimed to investigate the spatial and the temporal variability of N2O concentrations at different scales in the surface groundwater of a denitrifying aquifer in northern Germany. The spatial variability of N2O concentrations in the surface groundwater was analysed at the plot (200 × 200 m) and at the transect scale (12 m). Twenty plots that were distributed across an area of 11 km2 and 6 transects were sampled. Sixty per cent of the spatial variance of N2O was located at the plot scale and 68-79% was located at the transect scale. This indicates that small-scale processes governed the spatial variability of N2O in the surface groundwater. A spatial upscaling of N2O from the transect to the aquifer scale might be possible with an adequate number of samples that represent important boundary conditions for N2O accumulation in the catchment (topography, groundwater level, land use). For the investigation of the temporal variability, 4 multilevel wells were sampled monthly over a period of 13 months. In two periods, a multilevel well was additionally sampled in 2-day intervals over 8 days. At the annual scale, N2O concentrations in the surface groundwater were higher during the vegetation period (median 87 μg N2O-N l-1) and could change rapidly on the day scale whereas the concentrations were smaller in winter (median 21 μg N2O-N l-1). Groundwater recharge events seemed to be crucial for the day scale variability. Capture of the temporal variations for upscaling might be achieved with a process-based sampling strategy with weekly sampling intervals during the vegetation period, the additional sampling after groundwater recharge events and monthly sampling intervals in winter.

KW - Groundwater

KW - NO

KW - Spatial variability

KW - Temporal variability

KW - Upscaling

UR - http://www.scopus.com/inward/record.url?scp=77953027049&partnerID=8YFLogxK

U2 - 10.1007/s10705-009-9310-7

DO - 10.1007/s10705-009-9310-7

M3 - Article

AN - SCOPUS:77953027049

VL - 87

SP - 33

EP - 47

JO - Nutrient cycling in agroecosystems

JF - Nutrient cycling in agroecosystems

SN - 1385-1314

IS - 1

ER -