Transport Zonation Limits Coupled Nitrification-Denitrification in Permeable Sediments

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• 作者：Adam J. Kessler ; Ronnie N. Glud ; M. Bayani Cardenas ; Perran L. M. Cook
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：December 3, 2013
• 年：2013
• 卷：47
• 期：23
• 页码：13404-13411
• 全文大小：354K
• 年卷期：v.47,no.23(December 3, 2013)
• ISSN：1520-5851

文摘

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^{鈥?/sup> and 15N鈥揘₂ 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.}