Isotopic composition of nitrogen species in groundwater under agricultural areas: A review

Olha Nikolenko; Anna Jurado; Alberto V Borges; Kay Knӧller; Serge Brouyѐre

doi:10.1016/j.scitotenv.2017.10.086

Isotopic composition of nitrogen species in groundwater under agricultural areas: A review

Sci Total Environ. 2018 Apr 15:621:1415-1432. doi: 10.1016/j.scitotenv.2017.10.086. Epub 2017 Oct 23.

Authors

Olha Nikolenko¹, Anna Jurado², Alberto V Borges³, Kay Knӧller⁴, Serge Brouyѐre²

Affiliations

¹ University of Liѐge, ArGEnCo, Hydrogeology and Environmental Geology, Aquapôle, -B52/3 Sart-Tilman, 4000 Liѐge, Belgium. Electronic address: o.nikolenko@ulg.ac.be.
² University of Liѐge, ArGEnCo, Hydrogeology and Environmental Geology, Aquapôle, -B52/3 Sart-Tilman, 4000 Liѐge, Belgium.
³ Chemical Oceanography Unit, University of Liѐge, Liѐge, Belgium.
⁴ Department of Catchment Hydrology, UFZ Helmholtz - Centre for Environmental Research, Germany.

PMID: 29074237
DOI: 10.1016/j.scitotenv.2017.10.086

Abstract

This work reviews applications of stable isotope analysis to the studies of transport and transformation of N species in groundwater under agricultural areas. It summarizes evidence regarding factors affecting the isotopic composition of NO₃^-, NH₄⁺ and N₂O in subsurface, and discusses the use of ¹¹B, ¹⁸O, ¹³C, ³⁴S, ⁸⁷Sr/⁸⁶Sr isotopes to support the analysis of δ¹⁵N values. The isotopic composition of NO₃^-, NH₄⁺ and N₂O varies depending on their sources and dynamics of N cycle processes. The reported δ¹⁵N-NO₃^- values for sources of NO₃^- are: soil organic N - +3‰-+8‰, mineral fertilizers - -8‰-+7‰; manure/household waste - +5‰ to +35‰. For NH₄⁺ sources, the isotopic signature ranges are: organic matter - +2.4-+4.1‰, rainwater - -13.4-+2.3‰, mineral fertilizers - -7.4-+5.1‰, household waste - +5-+9‰; animal manure - +8-+11‰. For N₂O, isotopic composition depends on isotopic signatures of substrate pools and reaction rates. δ¹⁵N values of NO₃^- are influenced by fractionation effects occurring during denitrification (ɛ=5-40‰), nitrification (ɛ=5-35‰) and DNRA (ɛ not reported). The isotopic signature of NH₄⁺ is also affected by nitrification and DNRA as well as mineralization (ɛ=1‰), sorption (ɛ=1-8‰), anammox (ɛ=4.3-7.4‰) and volatilization (ɛ=25‰). As for the N₂O, production of N₂O leads to its depletion in ¹⁵N, whereas consumption - to enrichment in ¹⁵N. The magnitude of fractionation effects occurring during the considered processes depends on temperature, pH, DO, C/NO₃^- ratio, size of the substrate pool, availability of electron donors, water content in subsoil, residence time, land use, hydrogeology. While previous studies have accumulated rich data on isotopic composition of NO₃^- in groundwater, evidence remains scarce in the cases of NH₄⁺ and N₂O. Further research is required to consider variability of δ¹⁵N-NH₄⁺ and δ¹⁵N-N₂O in groundwater across agricultural ecosystems.

Keywords: Agriculture; Groundwater pollution; N anthropogenic sources; N cycle processes; N isotopes; Stable isotope analysis.

Publication types

Review