, Volume 111, Issue 1–3, pp 535–554 | Cite as

Dominance of biologically produced nitrate in upland waters of Great Britain indicated by stable isotopes

  • Chris J. CurtisEmail author
  • Timothy H. E. Heaton
  • Gavin L. Simpson
  • Chris D. Evans
  • James Shilland
  • Simon Turner


Atmospheric deposition of nitrogen (N) compounds is the major source of anthropogenic N to most upland ecosystems, where leaching of nitrate (NO 3 ) into surface waters contributes to eutrophication and acidification as well as indicating an excess of N in the terrestrial catchment ecosystems. Natural abundance stable isotopes ratios, 15N/14N and 18O/16O (the “dual isotope” technique) have previously been used in biogeochemical studies of alpine and forested ecosystems to demonstrate that most of the NO 3 in upland surface waters has been microbially produced. Here we present an application of the technique to four moorland catchments in the British uplands including a comparison of lakes and their stream inflows at two sites. The NO 3 concentrations of bulk deposition and surface waters at three sites are very similar. While noting the constraints imposed by uncertainty in the precise δ18O value for microbial NO 3 , however, we estimate that 79–98% of the annual mean NO 3 has been microbially produced. Direct leaching of atmospheric NO 3 is a minor component of catchment NO 3 export, although greater than in many similar studies in forested watersheds. A greater proportion of atmospheric NO 3 is seen in the two lake sites relative to their inflow streams, demonstrating the importance of direct NO 3 deposition to lake surfaces in catchments where terrestrial ecosystems intercept a large proportion of deposited N. The dominance of microbial sources of NO 3 in upland waters suggests that reduced and oxidised N deposition may have similar implications in terms of contributing to NO 3 leaching.


Nitrate leaching Nitrification 1815Uplands Lakes N deposition 



This work was funded by the UK Department for Environment, Transport and Rural Affairs (Defra) Contract CPEA17. Additional data were provided by the UK Acid Waters Monitoring Network and the UK Acid Deposition Monitoring Network. We thank the many colleagues in the ECRC who helped with fieldwork and Cath D’Alton of the Geography Department Drawing Office at UCL for vastly improving the figures.

Supplementary material

10533_2011_9686_MOESM1_ESM.doc (336 kb)
Supplementary material 1 (DOC 335 kb)


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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Chris J. Curtis
    • 1
    Email author
  • Timothy H. E. Heaton
    • 2
  • Gavin L. Simpson
    • 1
  • Chris D. Evans
    • 3
  • James Shilland
    • 1
  • Simon Turner
    • 1
  1. 1.Environmental Change Research Centre, Geography DepartmentUniversity College LondonLondonUK
  2. 2.NERC Isotope Geosciences LaboratoryBritish Geological SurveyNottinghamUK
  3. 3.Centre for Ecology and HydrologyEnvironment Centre WalesWalesUK

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