title: Perturbation-free measurement of in situ di-nitrogen emissions from denitrification in nitrate-rich aquatic ecosystems.
abstract: Increased production of reactive nitrogen (Nr) from atmospheric di-nitrogen (N2) has greatly contributed to increased food production. However, enriching the biosphere with Nr has also caused a series of negative effects on global ecosystems, especially aquatic ecosystems. The main pathway converting Nr back into the atmospheric N2pool is the last step in the denitrification process. Despite several attempts, there is still a need for perturbation-free methods for measuring in situ N2fluxes from denitrification in aquatic ecosystems at the field scale. Such a method is needed to comprehensively quantify the N2fluxes from aquatic ecosystems. Here we observed linear relationships between the δ15N-N2O signatures and the logarithmically transformed N2O/(N2+N2O) emission ratios. Through independent measurements, we verified that the perturbation-free N2flux from denitrification in nitrate-rich aquatic ecosystems can be inferred from these linear relationships. Our method allowed the determination of field-scale in situ N2fluxes from nitrate-rich aquatic ecosystems both with and without overlaying water. The perturbation-free in situ N2fluxes observed by the new method were almost one order of magnitude higher than those by the sediment core method. The ability of aquatic ecosystems to remove Nr may previously have been severely underestimated.
authors.affiliation: Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, The Chinese Academy of Sciences, 286 Huaizhong Road, Shijiazhuang, 050021, Hebei, China; Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
authors.forename: Shuping
authors.initials: S
authors.lastname: Qin
authors.affiliation: Lincoln University, Department of Agriculture & Life Sciences, Lincoln, New Zealand.
authors.forename: Timothy
authors.initials: T
authors.lastname: Clough
authors.affiliation: Land and Environment, AgResearch, Hamilton, 3240, New Zealand.
authors.forename: Jiafa
authors.initials: J
authors.lastname: Luo
authors.affiliation: University of Rostock, Department of Agriculture and The Environment, Grassland and Fodder Sciences, Rostock, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Wrage-Mönnig
authors.affiliation: Wageningen University and Research, Alterra, Wageningen, The Netherlands.
authors.forename: Oene
authors.initials: O
authors.lastname: Oenema
authors.affiliation: Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, The Chinese Academy of Sciences, 286 Huaizhong Road, Shijiazhuang, 050021, Hebei, China.
authors.forename: Yuming
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, The Chinese Academy of Sciences, 286 Huaizhong Road, Shijiazhuang, 050021, Hebei, China. Electronic address: meimei841114@163.com.
authors.forename: Chunsheng
authors.initials: C
authors.lastname: Hu
mesh_terms: D058440:Denitrification; D017753:Ecosystem; D009566:Nitrates; D009584:Nitrogen; D009609:Nitrous Oxide
chemical_list: D009566:Nitrates; D009609:Nitrous Oxide; D009584:Nitrogen
keywords: Denitrification; Isotopic fractionation; N(2)O reduction; Nitrogen loss; Reactive nitrogen