title: Combining Denitrifying Bacteria and Laser Spectroscopy for Isotopic Analyses (δ(15)N, δ(18)O) of Dissolved Nitrate.
abstract: We present a novel approach for nitrogen (δ(15)N) and oxygen (δ(18)O) isotopic analysis of nitrate in water based on the isotopic analysis of N2O produced from the conversion of NO3(-) by cultured denitrifying bacteria and off-axis integrated cavity output spectroscopy (OA-ICOS). The headspace N2O was manually injected into an OA-ICOS isotopic N2O laser analyzer through a syringe septum port. Sample analysis time was ∼300 s. The use of OA-ICOS technology yields accurate and precise δ(15)N and δ(18)O results for dissolved nitrate samples when nonlinearity issues are considered. This new isotope analytical technique thus improves the isotopic analysis of nitrates by (i) providing accurate measurements of δ(15)N and δ(18)O without preconcentration, (ii) eliminating interferences by other gas substances (i.e., H2O and CO2), and (iii) reducing extensive maintenance and costs of isotope ratio mass spectrometers (IRMS). This approach will greatly streamline the identification and quantification of nitrate sources in aquatic systems.
authors.affiliation: †Environment Canada, 11 Innovation Boulevard, Saskatoon, Saskatchewan, Canada, S7N 3H5.
authors.forename: David X
authors.initials: DX
authors.lastname: Soto
authors.affiliation: †Environment Canada, 11 Innovation Boulevard, Saskatoon, Saskatchewan, Canada, S7N 3H5.
authors.forename: Geoff
authors.initials: G
authors.lastname: Koehler
authors.affiliation: †Environment Canada, 11 Innovation Boulevard, Saskatoon, Saskatchewan, Canada, S7N 3H5.
authors.forename: Keith A
authors.initials: KA
authors.lastname: Hobson
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D013058:Mass Spectrometry; D009566:Nitrates / Q000032:analysis*; D009587:Nitrogen Isotopes / Q000737:chemistry; D009589:Nitrogen Oxides / Q000737:chemistry; D010103:Oxygen Isotopes / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D009566:Nitrates; D009587:Nitrogen Isotopes; D009589:Nitrogen Oxides; D010103:Oxygen Isotopes; D014867:Water