Fine-scale in situ measurement of riverbed nitrate production and consumption in an armored permeable riverbed

Research output: Contribution to journalArticlepeer-review

Authors

  • Katrina Lansdown
  • Catherine M. Heppell
  • Matteo Dossena
  • A. Louise Heathwaite
  • Andrew Binley
  • Hao Zhang
  • Mark Trimmer

Colleges, School and Institutes

External organisations

  • School of Biological and Chemical Sciences Queen Mary University of London
  • Queen Mary University of London
  • Lancaster University

Abstract

Alteration of the global nitrogen cycle by man has increased nitrogen loading in waterways considerably, often with harmful consequences for aquatic ecosystems. Dynamic redox conditions within riverbeds support a variety of nitrogen transformations, some of which can attenuate this burden. In reality, however, assessing the importance of processes besides perhaps denitrification is difficult, due to a sparseness of data, especially in situ, where sediment structure and hydrologic pathways are intact. Here we show in situ within a permeable riverbed, through injections of 15N-labeled substrates, that nitrate can be either consumed through denitrification or produced through nitrification, at a previously unresolved fine (centimeter) scale. Nitrification and denitrification occupy different niches in the riverbed, with denitrification occurring across a broad chemical gradient while nitrification is restricted to more oxic sediments. The narrow niche width for nitrification is in effect a break point, with the switch from activity "on" to activity "off" regulated by interactions between subsurface chemistry and hydrology. Although maxima for denitrification and nitrification occur at opposing ends of a chemical gradient, high potentials for both nitrate production and consumption can overlap when groundwater upwelling is strong.

Details

Original languageEnglish
Pages (from-to)4425-4434
Number of pages10
JournalEnvironmental Science and Technology
Volume48
Issue number8
Early online date16 Mar 2014
Publication statusPublished - 15 Apr 2014

ASJC Scopus subject areas