Nitrite consumption and associated isotope changes during a river flood event in the Elbe river, supplement to: Jacob, Juliane; Sanders, Tina; Dähnke, Kirstin (2016): Nitrification and Nitrite Isotope Fractionation as a Case Study in a major European River. Biogeosciences, 13(19), 5649-5659

DOI

In oceans, estuaries, and rivers, nitrification is an important nitrate source, and stable isotopes of nitrate are often used to investigate recycling processes (e.g. remineralisation, nitrification) in the water column. Nitrification is a two-step process, where ammonia is oxidised via nitrite to nitrate. Nitrite usually does not accumulate in natural environments, which makes it difficult to study the single isotope effect of ammonia oxidation or nitrite oxidation in natural systems. However, during an exceptional flood in the Elbe River in June 2013, we found a unique co-occurrence of ammonium, nitrite, and nitrate in the water column, returning towards normal summer conditions within 1 week. Over the course of the flood, we analysed the evolution of d15N-[NH4]+ and d15N-[NO2]- in the Elbe River. In concert with changes in suspended particulate matter (SPM) and d15N SPM, as well as nitrate concentration, d15N-NO3 - and d18O-[NO3] -, we calculated apparent isotope effects during net nitrite and nitrate consumption. 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, respectively, likely due to remineralisation, nitrification, and denitrification in the water column. d15N-[NH4]+ values increased up to 12 per mil, and d15N-[NO2]- ranged from -8.0 to -14.2 per mil. Based on this, we calculated an apparent isotope effect 15-epsilon of -10.0 ± 0.1 per mil during net nitrite consumption, as well as an isotope effect 15-epsilon of -4.0 ± 0.1 per mil and 18-epsilon of -5.3 ± 0.1 per mil 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. The objectives of this project were to identify the key processes in the nitrogen cycle in the estuarine and coastal waters using stable N isotopes and to quantify these processes. As parameter the nutrient loads and stable isotopes values of nitrogen were measured.

Identifier
DOI https://doi.org/10.1594/PANGAEA.865348
Related Identifier https://doi.org/10.5194/bg-13-5649-2016
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.865348
Provenance
Creator Jacob, Juliane; Sanders, Tina; Dähnke, Kirstin
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Contributor Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research
Publication Year 2016
Rights Creative Commons Attribution 3.0 Unported
OpenAccess true
Representation
Language English
Resource Type Supplementary Dataset
Format text/tab-separated-values
Size 443 data points
Discipline Earth System Research
Spatial Coverage (10.336 LON, 53.425 LAT); Geesthacht weir, Germany
Temporal Coverage Begin 2013-06-06T10:08:00Z
Temporal Coverage End 2013-06-20T09:25:00Z