『Abstract
　Different models for calculate on of di-nitrogen fluxes using ¹⁵NO3 tracers were tested for their congruence with experimental data obtained with marine sediment samples. The co-occurrence of nitrification as source of substrate and the simultaneous N2 production from denitrification and/or Anammox were taken into account as well as nitrous oxide production in the total denitrification rate. The results highlighted that isotope technique provides a powerful tool to evaluate, in the same experimental set up, the rates of total N2 fluxes: denitrification and/or Anammox if it is carefully applied and its limitations, mainly the range of ¹⁵NO3 inputs are adapted to the studied samples and the linearity of the kinetics of the products checked.

Keywords: Anammox; Denitrification; Nitrification; Nitrous oxide; Isotope pairing method; Simulation』

Introduction
Materials and methods
　Sampling site
　Sediment incubations experiments
　N2 and N2O isotope measurements with quadruple mass spectrometry
　Modelling the behaviour of di-nitrogen production
　Nitrification rates
　Statistical analyses
Results
　Determination of N2 production in the presence of denitrification only: the original method of Nielsen
　Determination of N2 production from denitrification in the presence of nitrification
　Determination of N2 production in the presence of denitrification and Anammox
　Determination of total denitrification taking into account N2O accumulation
Discussion and conclusions
Acknowledgements
References