%0 journal article
%@ 1726-4170
%A Jacob, J., Sanders, T., Daehnke, K.

%D 2016
%J Biogeosciences
%N 19
%P 5649-5659 
%R doi:10.5194/bg-13-5649-2016
%T Nitrite consumption and associated isotope changes during a river flood event
%U https://doi.org/10.5194/bg-13-5649-2016
19 
%X During the flood event, > 97 % of total reactive nitrogen was nitrate, which was leached from the catchment area and appeared to be subject to assimilation. Ammonium and nitrite concentrations increased to 3.4 and 4.4 µmol L−1, respectively, likely due to remineralisation, nitrification, and denitrification in the water column. δ15N–NH4+ values increased up to 12 ‰, and δ15N–NO2− ranged from −8.0 to −14.2 ‰. Based on this, we calculated an apparent isotope effect 15ε of −10.0 ± 0.1 ‰ during net nitrite consumption, as well as an isotope effect 15ε of −4.0 ± 0.1 ‰ and 18ε of −5.3 ± 0.1 ‰ during net nitrate consumption. On the basis of the observed nitrite isotope changes, we evaluated different nitrite uptake processes in a simple box model. We found that a regime of combined riparian denitrification and 22 to 36 % nitrification fits best with measured data for the nitrite concentration decrease and isotope increase.