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Rapid immobilisation and leaching of wet-deposited nitrate in upland organic soils

Research output: Contribution to journalJournal articlepeer-review

Published
  • Chris D. Evans
  • Dave Norris
  • Nick Ostle
  • Helen Grant
  • Edwin C. Rowe
  • Chris J. Curtis
  • Brian Reynolds
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<mark>Journal publication date</mark>1/12/2008
<mark>Journal</mark>Environmental Pollution
Issue number3
Volume156
Number of pages8
Pages (from-to)636-643
Publication StatusPublished
Early online date23/07/08
<mark>Original language</mark>English

Abstract

Nitrate (NO3-) is often observed in surface waters draining terrestrial ecosystems that remain strongly nitrogen (N) limited. It has been suggested that this occurs due to hydrological bypassing of soil or vegetation N retention, particularly during high flows. To test this hypothesis, artificial rain events were applied to 12 replicate soil blocks on a Welsh podzolic acid grassland hillslope, labelled with 15N-enriched NO3- and a conservative bromide (Br-) tracer. On average, 31% of tracer-labelled water was recovered within 4 h, mostly as mineral horizon lateral flow, indicating rapid vertical water transfer through the organic horizon via preferential flowpaths. However, on average only 6% of 15N-labelled NO3- was recovered. Around 80% of added NO3- was thus rapidly immobilised, probably by microbial communities present on the surfaces of preferential flowpaths. Transitory exceedance of microbial N-uptake capacity during periods of high water and N flux may therefore provide a mechanism for NO3- leaching.