Transport Zonation Limits Coupled Nitrification-Denitrification in Permeable Sediments

Measurement of biogeochemical processes in permeable sediments (including the hyporheic zone) is difficult because of complex multidimensional advective transport. This is especially the case for nitrogen cycling, which involves several coupled redox-sensitive reactions. To provide detailed insight...

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Bibliographic Details
Published in:Environmental science & technology 2013-12, Vol.47 (23), p.13404-13411
Main Authors: Kessler, Adam J, Glud, Ronnie N, Cardenas, M. Bayani, Cook, Perran L. M
Format: Article
Language:English
Subjects:
Biogeochemistry
Denitrification
Diffusion
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Exact sciences and technology
Geologic Sediments
Marine and continental quaternary
Models, Theoretical
Nitrification
Nitrogen - analysis
Oxidation-Reduction
Pollution, environment geology
Sediment transport
Sediments
Surficial geology
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Summary:Measurement of biogeochemical processes in permeable sediments (including the hyporheic zone) is difficult because of complex multidimensional advective transport. This is especially the case for nitrogen cycling, which involves several coupled redox-sensitive reactions. To provide detailed insight into the coupling between ammonification, nitrification and denitrification in stationary sand ripples, we combined the diffusion equilibrium thin layer (DET) gel technique with a computational reactive transport biogeochemical model. The former approach provided high-resolution two-dimensional distributions of NO3 – and 15N–N2 gas. The measured two-dimensional profiles correlate with computational model simulations, showing a deep pool of N2 gas forming, and being advected to the surface below ripple peaks. Further isotope pairing calculations on these data indicate that coupled nitrification-denitrification is severely limited in permeable sediments because the flow and transport field limits interaction between oxic and anoxic pore water. The approach allowed for new detailed insight into subsurface denitrification zones in complex permeable sediments.
ISSN:0013-936X
1520-5851
DOI:10.1021/es403318x