Sebilo, MathieuAloisi, GiovanniMayer, BernhardPerrin, EmilieVaury, VéroniqueMothet, AurélieLaverman, Anniet M2022-09-022022-09-022019-12-16Sebilo, M., Aloisi, G., Mayer, B., Perrin, E., Vaury, V., Mothet, A., & Laverman, A. M. (2019). Controls on the Isotopic Composition of Nitrite (δ15N and δ18O) during Denitrification in Freshwater Sediments. Scientific Reports, 9(1), 19206. https://doi.org/10.1038/s41598-019-54014-32045-2322http://hdl.handle.net/1880/115158https://doi.org/10.11575/PRISM/46074The microbial reduction of nitrate, via nitrite into gaseous di-nitrogen (denitrification) plays a major role in nitrogen removal from aquatic ecosystems. Natural abundance stable isotope measurements can reveal insights into the dynamics of production and consumption of nitrite during denitrification. In this study, batch experiments with environmental bacterial communities were used to investigate variations of concentrations and isotope compositions of both nitrite and nitrate under anoxic conditions. To this end, denitrification experiments were carried out with nitrite or nitrate as sole electron acceptors at two substrate levels respectively. For experiments with nitrate as substrate, where the intermediate compound nitrite is both substrate and product of denitrification, calculations of the extent of isotope fractionation were conducted using a non-steady state model capable of tracing chemical and isotope kinetics during denitrification. This study showed that nitrogen isotope fractionation was lower during the use of nitrite as substrate (ε = -4.2 and -4.5‰ for both treatments) as compared to experiments where nitrite was produced as an intermediate during nitrate reduction (ε = -10 and -15‰ for both treatments). This discrepancy might be due to isotopic fractionation within the membrane of denitrifiers. Moreover, our results confirmed previously observed rapid biotic oxygen isotope exchange between nitrite and water.engUnless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.Analytical chemistryChemical SciencesDenitrificationElement cyclesExperimentsIsotopesMaterial chemistryNitratesNitrogenPolymersSedimentsjournal articlehttp://dx.doi.org/10.1038/s41598-019-54014-3