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The role of catchment characteristics in determining surface water nitrogen in four upland regions in the UK

Helliwell, R. C.; Coull, M. C.; Davie, J. J. L.; Evans, C. D.; Norris, D.; Ferrier, R. C.; Jenkins, A.; Reynolds, B.. 2007 The role of catchment characteristics in determining surface water nitrogen in four upland regions in the UK. Hydrology and Earth System Sciences, 11 (1). 356-371.

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Abstract/Summary

Hydrochemical and catchment data from 80 upland moorland sites in four regions with contrasting climate, soils, geology and geomorphology have been analysed to assess the key catchment attributes that influence enhanced leaching of soluble nitrogen to surface waters. The regions are the South Pennines of northern England, the Snowdonia National Park in north Wales, the Galloway region of south-west Scotland and the Mourne Mountains in Northern Ireland, all highly acidified, with median pH values of <5.5. Linear regression of mean summer and winter concentrations for nitrate (NO3−), ammonium (NH4+), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) were expressed as functions of catchment attributes. Nitrate concentrations in waters draining catchments dominated by peaty soils (large C pool) were much less than those in catchments dominated by mineral soils (small C pool). Hence, if future N deposition levels are maintained or increase, high-altitude catchments with small carbon pools are potentially more susceptible to NO3− leaching. All N species exhibit seasonality; this is most marked in Galloway and least marked in the South Pennines, which implies that the South Pennines have reached an advanced stage of N saturation. Surface water inorganic N concentrations and the ratio of dissolved organic carbon (DOC) to dissolved organic N (DON) can be related to deposition inputs, although relationships differ throughout the year. If the DOC/DON ratio is indicative of catchment N saturation, levels of N retention are at least partially determined by deposition levels. This study identifies N deposition as a major inter-regional control on the degree of catchment N saturation and on N leaching to surface waters; it stresses the importance of catchment factors in modifying the relationship between N deposition and leaching in acid sensitive UK upland catchments.

Item Type: Publication - Article
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry
CEH Programmes pre-2009 publications > Water
CEH Sections: Emmett
ISSN: 1027-5606
Additional Keywords: seasonal nitrogen deposition and leaching, catchment characteristics, South Pennines, Snowdonia, Galloway, Mourne Mountains
NORA Subject Terms: Agriculture and Soil Science
Ecology and Environment
Hydrology
Date made live: 22 Jan 2008 14:17
URI: http://nora.nerc.ac.uk/id/eprint/1771

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