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13 - Nitrogen flows from European regional watersheds to coastal marine waters
- from Part III - Nitrogen flows and fate at multiple spatial scales
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- By Gilles Billen, University Pierre & Marie Curie, Marie Silvestre, CNRS – FR3020 FIRE, Bruna Grizzetti, European Commission Joint Research Centre, Adrian Leip, European Commission Joint Research Centre, Josette Garnier, UMR Sisyphe UPMC & CNRS, Maren Voss, Leibniz-Institute of Baltic Sea Research Warnemuende, Robert Howarth, Cornell University, Fayçal Bouraoui, European Commission Joint Research Centre, Ahti Lepistö, Finnish Environment Institute, Pirkko Kortelainen, Finnish Environment Institute, Penny Johnes, University of Reading, Chris Curtis, University College London Environmental Change Research Centre, Christoph Humborg, Stockholm University, Erik Smedberg, Stockholm University, Øyvind Kaste, Norwegian Institute for Water Research, Raja Ganeshram, University of Edinburgh, Arthur Beusen, Netherlands Environmental Assessment Agency, Christiane Lancelot, Université Libre de Bruxelles
- Edited by Mark A. Sutton, NERC Centre for Ecology and Hydrology, UK, Clare M. Howard, NERC Centre for Ecology and Hydrology, UK, Jan Willem Erisman, Gilles Billen, Albert Bleeker, Peringe Grennfelt, Hans van Grinsven, Bruna Grizzetti
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- Book:
- The European Nitrogen Assessment
- Published online:
- 16 May 2011
- Print publication:
- 14 April 2011, pp 271-297
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- Chapter
- Export citation
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Summary
Executive summary
Nature of the problem
Most regional watersheds in Europe constitute managed human territories importing large amounts of new reactive nitrogen.
As a consequence, groundwater, surface freshwater and coastal seawater are undergoing severe nitrogen contamination and/or eutrophication problems.
Approaches
A comprehensive evaluation of net anthropogenic inputs of reactive nitrogen (NANI) through atmospheric deposition, crop N fixation, fertiliser use and import of food and feed has been carried out for all European watersheds. A database on N, P and Si fluxes delivered at the basin outlets has been assembled.
A number of modelling approaches based on either statistical regression analysis or mechanistic description of the processes involved in nitrogen transfer and transformations have been developed for relating N inputs to watersheds to outputs into coastal marine ecosystems.
Key findings/state of knowledge
Throughout Europe, NANI represents 3700 kgN/km²/yr (range, 0–8400 depending on the watershed), i.e. five times the background rate of natural N2 fixation.
A mean of approximately 78% of NANI does not reach the basin outlet, but instead is stored (in soils, sediments or ground water) or eliminated to the atmosphere as reactive N forms or as N2.
N delivery to the European marine coastal zone totals 810 kgN/km²/yr (range, 200–4000 depending on the watershed), about four times the natural background. In areas of limited availability of silica, these inputs cause harmful algal blooms.