NDLI: Reaction chain modeling of denitrification reactions during a push-pull test.

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Boisson, A. de Anna, P. Bour, O. Le Borgne, T. Labasque, T. Aquilina, L.
Description	Country affiliation: France Author Affiliation: Boisson A ( Géosciences Rennes-OSUR, UMR CNRS 6118, University of Rennes 1, France. a.boisson@brgm.fr)
Abstract	Field quantitative estimation of reaction kinetics is required to enhance our understanding of biogeochemical reactions in aquifers. We extended the analytical solution developed by Haggerty et al. (1998) to model an entire 1st order reaction chain and estimate the kinetic parameters for each reaction step of the denitrification process. We then assessed the ability of this reaction chain to model biogeochemical reactions by comparing it with experimental results from a push-pull test in a fractured crystalline aquifer (Ploemeur, French Brittany). Nitrates were used as the reactive tracer, since denitrification involves the sequential reduction of nitrates to nitrogen gas through a chain reaction (NO3(-)âNO2(-)âNOâN2OâN2) under anaerobic conditions. The kinetics of nitrate consumption and by-product formation (NO2(-), N2O) during autotrophic denitrification were quantified by using a reactive tracer (NO3(-)) and a non-reactive tracer (Br(-)). The formation of reaction by-products (NO2(-), N2O, N2) has not been previously considered using a reaction chain approach. Comparison of Br(-) and NO3(-) breakthrough curves showed that 10% of the injected NO3(-) molar mass was transformed during the 12 h experiment (2% into NO2(-), 1% into N2O and the rest into N2 and NO). Similar results, but with slower kinetics, were obtained from laboratory experiments in reactors. The good agreement between the model and the field data shows that the complete denitrification process can be efficiently modeled as a sequence of first order reactions. The 1st order kinetics coefficients obtained through modeling were as follows: k1=0.023 h(-1), k2=0.59 h(-1), k3=16 h(-1), and k4=5.5 h(-1). A next step will be to assess the variability of field reactivity using the methodology developed for modeling push-pull tracer tests.
File Format	HTM / HTML
ISSN	01697722
Volume Number	148
e-ISSN	18736009
Journal	Journal of Contaminant Hydrology
Language	English
Publisher	Elsevier
Publisher Date	2013-05-01
Publisher Place	Netherlands
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Discipline Chemistry Discipline Toxicology Denitrification Environmental Monitoring Methods Groundwater Chemistry Nitrates Metabolism Autotrophic Processes Kinetics Models, Theoretical Nitrogen Nitrous Oxide Oxidation-reduction Evaluation Studies Journal Article Research Support, Non-u.s. Gov't
Content Type	Text
Resource Type	Article
Subject	Environmental Chemistry Water Science and Technology

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