Determination of the δ15N and δ18O of nitrate in water; RSIL lab code 2900
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Abstract
NO3- → NO2- → NO → 1/2 N2O (1)
Because the bacteria Pseudomonas aureofaciens lack N2O reductive activity, the reaction stops at N2O, unlike the typical denitrification reaction that goes to N2. After several hours, the conversion is complete, and the N2O is extracted from the vial, separated from volatile organic vapor and water vapor by an automated -65 °C isopropanol-slush trap, a Nafion drier, a CO2 and water removal unit (Costech #021020 carbon dioxide absorbent with Mg(ClO4)2), and trapped in a small-volume trap immersed in liquid nitrogen with a modified Finnigan MAT (now Thermo Scientific) GasBench 2 introduction system. After the N2O is released, it is further purified by gas chromatography before introduction to the isotope-ratio mass spectrometer (IRMS). The IRMS is a Thermo Scientific Delta V Plus continuous flow IRMS (CF-IRMS). It has a universal triple collector, consisting of two wide cups with a narrow cup in the middle; it is capable of simultaneously measuring mass/charge (m/z) of the N2O molecule 44, 45, and 46. The ion beams from these m/z values are as follows: m/z = 44 = N2O = 14N14N16O; m/z = 45 = N2O = 14N15N16O or 14N14N17O; m/z = 46 = N2O = 14N14N18O. The 17O contributions to the m/z 44 and m/z 45 ion beams are accounted for before δ15N values are reported.Publication type | Report |
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Publication Subtype | USGS Numbered Series |
Title | Determination of the δ15N and δ18O of nitrate in water; RSIL lab code 2900 |
Series title | Techniques and Methods |
Series number | 10-C17 |
DOI | 10.3133/tm10C17 |
Edition | Version 1.0 - 2007, Version 1.1 - September 2012 |
Year Published | 2007 |
Language | English |
Publisher | U.S. Geological Survey |
Publisher location | Reston, VA |
Contributing office(s) | Reston Stable Isotope Laboratory |
Description | viii, 35 p. |
Larger Work Type | Report |
Larger Work Subtype | USGS Numbered Series |
Larger Work Title | Chapter 17 of Section C: Stable Isotope-Ratio Methods, Book 10: Methods of the Reston Stable Isotope Laboratory |
Online Only (Y/N) | Y |
Google Analytic Metrics | Metrics page |