『Abstract
　Tidal freshwater zones (TFZ) of coastal rivers link terrestrial watersheds to the ocean and are characterized by large, regularly inundated riparian zones. We investigated the effect of riparian denitrification on nitrogen flux in the TFZ Newport River, North Carolina (U.S.A.) by developing an empirical model of denitrification and parameterizing it using measured denitrification rates, sediment oxidation-reduction potential dynamics, and riparian topography. Denitrification rates were measured monthly in laboratory-incubated sediment cores by using a membrane inlet mass spectrometer to assess net water-borne N2 flux from the cores. annual average rates of denitrification in three intertidal riparian habitats, emergent marsh, mudflat, and hardwood forest, were 1864, 1956, and 2018μg m^-2 h^-1, respectively. Laboratory experiments and in-situ monitoring revealed that the temporal lag between tidal inundation and reduced, denitrifying conditions was 4-5 h. Field measurements and remotely sensed data showed that the inundated surface area during high tide was three times greater than that at low tide. By combining data on denitrification, oxidation-reduction potential, and topography, the model predicted that the daily denitrification flux constituted 2-15％ of the daily riverine nitrate flux during most of the year and ＞100％ during low discharge periods. Current regional and global nitrogen budgets thus may overestimate nitrogen delivery to the ocean by not accounting for the TFZ denitrification.

Keywords: Denitrification; Tidal freshwater zone; Riparian floodplain; River nitrogen budget』

Abbreviations
Introduction
Riparian zone denitrification model
Site description
Materials and methods
　Riparian zone denitrification
　Riparian zone oxidation-reduction potential
　Laboratory oxidation-reduction potential experiments
　Channel bathymetry and riparian zone topography
　Tidal freshwater river nitrogen load
　Riparian zone denitrification model
Results
　Riparian zone denitrification
　Riparian zone oxidation-reduction potential
　Laboratory oxidation-reduction potential experiments
　Channel bathymetry and riparian zone topography
　Tidal freshwater river nitrogen load
　Riparian zone denitrification model
Discussion
　Denitrification and redox dynamics in tidal freshwater river floodplains
　Uncertainties, future development, and application of the floodplain denitrification model
　How does riparian denitrification compare to in-channel denitrification?
Acknowledgments
References