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Longitudinal transformation of nitrogen and carbon in the hyporheic zone of an N-rich stream: A combined modelling and field study

Peyrard, Dimitri and Delmotte, Sébastien and Sauvage, Sabine and Namour, Philippe and Gérino, Magali and Vervier, Philippe and Sanchez-Pérez, José-Miguel Longitudinal transformation of nitrogen and carbon in the hyporheic zone of an N-rich stream: A combined modelling and field study. (2011) Physics and Chemistry of the Earth, vol. 36 (n° 12). pp. 599-611. ISSN 1474-7065

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Official URL: http://dx.doi.org/10.1016/j.pce.2011.05.003

Abstract

A combined modelling and field study approach was used to examine biogeochemical functioning of the hyporheic zone in two gravel bars in an N-rich fourth-order stream (River Hers, south-west France). Surfacewater and interstitial water were sampledmonthly (August 1994–January 1995), the latter in a network of 29 piezometers in the first gravel bar and 17 in the second. In both gravel bars, the hyporheic zone was created only by advected channelwater without any connectionwith groundwater. Longitudinal chemical profiles of Dissolved Organic Carbon (DOC), nitrate (NO3–N), ammonium (NH4–N) and Dissolved Oxygen (DO) were established for both gravel bars. Ambient and potential denitrification weremeasured in the laboratory during the same period using the acetylene inhibition technique. Factors limiting denitrification were also examined by testing the separate effects of nitrate or nitrate + carbon additions. A 1D reactive-transport model was used to simulate longitudinal transformation of nitrogen in the hyporheic zone, and to estimate the role of organic matter (DOC and POC) in the biogeochemical functioning of the hyporheic zone. Denitrification measurements with nitrate and nitrate + carbon additions both showed increased denitrification, suggesting that denitrification might not be C-limited at this site. Observations and model results showed the hyporheic zone to be a sink of DOC and nitrate, but DOC consumption appeared insufficient to explain nitrate depletion measured in the two gravel bars. Field data were better modelled when an additional DOC source from the POC fraction degraded by anaerobic respiration was included in the model.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
Other partners > Modélisation et Analyses de Données en Environnement - MAD-Environnement (FRANCE)
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
French research institutions > Institut national de recherche en sciences et technologies pour l’environnement et l’agriculture - CEMAGREF
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Deposited By: Nadia Kelmouss
Deposited On:01 Jun 2012 14:41

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