This Article Full Text Full Text (PDF) Other Versions of this Article: AEM.01442-06v1 73/1/40    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Laverman, A. M. Articles by Wieringa, E. B. A. Search for Related Content PubMed PubMed Citation Articles by Laverman, A. M. Articles by Wieringa, E. B. A. Agricola Articles by Laverman, A. M. Articles by Wieringa, E. B. A.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, January 2007, p. 40-47, Vol. 73, No. 1
0099-2240/07/$08.00+0     doi:10.1128/AEM.01442-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Vertical Distribution of Denitrification in an Estuarine Sediment: Integrating Sediment Flowthrough Reactor Experiments and Microprofiling via Reactive Transport Modeling

Department of Earth Sciences-Geochemistry, Utrecht University, Utrecht, The Netherlands,¹ Department of Marine Sciences, University of Georgia, Athens, Georgia,² Max Planck Institute for Marine Microbiology, Bremen, Germany³

Received 22 June 2006/ Accepted 13 October 2006

Denitrifying activity in a sediment from the freshwater part of a polluted estuary in northwest Europe was quantified using two independent approaches. High-resolution N₂O microprofiles were recorded in sediment cores to which acetylene was added to the overlying water and injected laterally into the sediment. The vertical distribution of the rate of denitrification supported by nitrate uptake from the overlying water was then derived from the time series N₂O concentration profiles. The rates obtained for the core incubations were compared to the rates predicted by a forward reactive transport model, which included rate expression for denitrification calibrated with potential rate measurements obtained in flowthrough reactors containing undisturbed, 1-cm-thick sediment slices. The two approaches yielded comparable rate profiles, with a near-surface, 2- to 3-mm narrow zone of denitrification and maximum in situ rates on the order of 200 to 300 nmol cm^–3 h^–1. The maximum in situ rates were about twofold lower than the maximum potential rate for the 0- to 1-cm depth interval of the sediment, indicating that in situ denitrification was nitrate limited. The experimentally and model-derived rates of denitrification implied that there was nitrate uptake by the sediment at a rate that was on the order of 50 (± 10) nmol cm^–2 h^–1, which agreed well with direct nitrate flux measurements for core incubations. Reactive transport model calculations showed that benthic uptake of nitrate at the site is particularly sensitive to the nitrate concentration in the overlying water and the maximum potential rate of denitrification in the sediment.

Published ahead of print on 27 October 2006.