Water, Air, & Soil Pollution: Focus

, Volume 4, Issue 6, pp 97–105 | Cite as

A conceptual model of spatially heterogeneous nitrogen leaching from a welsh moorland catchment

  • C. D. Evans
  • B. Reynolds
  • C. J. Curtis
  • H. D. Crook
  • D. Norris
  • S. A. Brittain
Article

Abstract

Soil- and stream-water data from the Plynlimon research area, mid-Wales, have been used to develop a conceptual model of spatial variations in nitrogen (N) leaching within moorland catchments. Extensive peats, in both hilltop and valley locations, are considered near-complete sinks for inorganic N, but leach the most dissolved organic nitrogen (DON). Peaty mineral soils on hillslopes also retain inorganic N within upper organic horizons, but a proportion percolates into mineral horizons as nitrate (NO 3 ), either through incomplete immobilisation in the organic layer, or in water bypassing the organic soil matrix via macropores. This NO 3 reaches the stream where mineral soilwaters discharge (via matrix throughflow or pipeflow) directly to the drainage network, or via small N-enriched flush wetlands. NO 3 in hillslope waters discharging into larger valley wetlands will be removed before reaching the stream. A concept of catchment ‘nitrate leaching zones’ is proposed, whereby most stream NO 3 derives from localised areas of mineral soil hillslope draining directly to the stream; the extent of these zones within a catchment may thus determine its overall susceptibility to elevated surface water NO 3 concentrations.

Keywords

hillslope hydrology immobilisation nitrate leaching zones nitrogen saturation 

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Copyright information

© Kluwer Academic Publishers 2004

Authors and Affiliations

  • C. D. Evans
    • 1
  • B. Reynolds
    • 1
  • C. J. Curtis
    • 2
  • H. D. Crook
    • 1
    • 3
  • D. Norris
    • 1
  • S. A. Brittain
    • 1
  1. 1.Centre for Ecology and HydrologyBangorUK
  2. 2.ECRC, University College LondonLondonUK
  3. 3.Department of Geography, School of Human and Environmental SciencesUniversity of ReadingWhiteknights, ReadingUK

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