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Nitrate transport and retention in Western European catchments are shaped by hydroclimate and subsurface properties
  • +3
  • Sophie Ehrhardt,
  • Pia Ebeling,
  • Rémi Dupas,
  • Rohini Kumar,
  • Jan Fleckenstein,
  • Andreas Musolff
Sophie Ehrhardt
Helmholtz Centre for Environmental Research, Helmholtz Centre for Environmental Research, Helmholtz Centre for Environmental Research, Helmholtz Centre for Environmental Research

Corresponding Author:[email protected]

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Pia Ebeling
UFZ - Helmholtz-Centre for Environmental Research, UFZ - Helmholtz-Centre for Environmental Research, UFZ - Helmholtz-Centre for Environmental Research, UFZ - Helmholtz-Centre for Environmental Research
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Rémi Dupas
INRAE, L'institut Agro, UMR 1069 SAS, 35000 Rennes, France, INRAE, L'institut Agro, UMR 1069 SAS, 35000 Rennes, France, INRAE, L'institut Agro, UMR 1069 SAS, 35000 Rennes, France, INRAE, L'institut Agro, UMR 1069 SAS, 35000 Rennes, France
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Rohini Kumar
UFZ-Helmholtz Centre for Environmental Research, UFZ-Helmholtz Centre for Environmental Research, UFZ-Helmholtz Centre for Environmental Research, UFZ-Helmholtz Centre for Environmental Research
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Jan Fleckenstein
Helmholtz Center for Environmental Research - UFZ, Helmholtz Center for Environmental Research - UFZ, Helmholtz Center for Environmental Research - UFZ, Helmholtz Center for Environmental Research - UFZ
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Andreas Musolff
UFZ - Helmholtz-Centre for Environmental Research, UFZ - Helmholtz-Centre for Environmental Research, UFZ - Helmholtz-Centre for Environmental Research, UFZ - Helmholtz-Centre for Environmental Research
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Abstract

Excess nitrogen (N) from anthropogenic sources deteriorates freshwater resources. Actions taken to reduce N inputs to the biosphere often show no or only delayed effects in receiving surface waters hinting at large legacy N stores built up in the catchments soils and groundwater. Here, we quantify transport and retention of N in 238 Western European catchments by analyzing a unique data set of long-term N input and output time series. We find that half of the catchments exhibited peak transport times larger than five years with longer times being evident in catchments with high potential evapotranspiration and low precipitation seasonality. On average the catchments retained 72% of the N from diffuse sources with retention efficiency being specifically high in catchments with low discharge and thick, unconsolidated aquifers. The estimated transport time scales do not explain the observed N retention, suggesting a dominant role of biogeochemical legacy in the catchments’ soils rather than a legacy store in the groundwater. Future water quality management should account for the accumulated biogeochemical N legacy to avoid long-term leaching and water quality deteriorations for decades to come.