title: A suite of sensitive chemical methods to determine the δ15N of ammonium, nitrate and total dissolved N in soil extracts.
abstract: Natural (15) N abundances (δ(15) N values) of different soil nitrogen pools deliver crucial information on the soil N cycle for the analysis of biogeochemical processes. Here we report on a complete suite of methods for sensitive δ(15) N analysis in soil extracts. A combined chemical reaction of vanadium(III) chloride (VCl(3) ) and sodium azide under acidic conditions is used to convert nitrate into N(2) O, which is subsequently analyzed by purge-and-trap isotope ratio mass spectrometry (PTIRMS) with a cryo-focusing unit. Coupled with preparation steps (microdiffusion for collection of ammonium, alkaline persulfate oxidation to convert total dissolved N (TDN) or ammonium into nitrate) this allows the determination of the δ(15) N values of nitrate, ammonium and total dissolved N (dissolved organic N, microbial biomass N) in soil extracts with the same basic protocol. The limits of quantification for δ(15) N analysis with a precision of 0.5‰ were 12.4 µM for ammonium, 23.7 µM for TDN, 16.5 µM for nitrate and 22.7 µM for nitrite.
authors.affiliation: Department of Chemical Ecology and Ecosystem Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria.
authors.forename: Petra
authors.initials: P
authors.lastname: Lachouani
authors.forename: Alexander H
authors.initials: AH
authors.lastname: Frank
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wanek
mesh_terms: D002712:Chlorides / Q000737:chemistry; D016014:Linear Models; D013058:Mass Spectrometry; D009566:Nitrates / Q000737:chemistry*; D009573:Nitrites / Q000737:chemistry; D009584:Nitrogen / Q000032:analysis* / Q000737:chemistry; D009587:Nitrogen Isotopes / Q000032:analysis* / Q000737:chemistry; D009609:Nitrous Oxide / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012987:Soil / Q000032:analysis*; D013997:Time Factors; D017968:Vanadium Compounds / Q000737:chemistry
chemical_list: D002712:Chlorides; D009566:Nitrates; D009573:Nitrites; D009587:Nitrogen Isotopes; D000644:Quaternary Ammonium Compounds; D012987:Soil; D017968:Vanadium Compounds; D009609:Nitrous Oxide; D009584:Nitrogen