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Automated, High-resolution Mobile Collection System for the Nitrogen Isotopic Analysis of NOx

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Published on: December 20, 2016

Oxygen isotopes in nitrite: analysis, calibration, and equilibration.

Karen L Casciotti¹, John Karl Böhlke, Matthew R McIlvin

¹US Geological Survey, Reston, Virginia 20192, USA. kcasciotti@whoi.edu

Analytical Chemistry

|February 14, 2007

Summary

Accurate oxygen isotope analysis of nitrite (NO2-) is crucial for understanding nitrogen cycling. This study extends the denitrifier method for nitrite isotope analysis and provides storage recommendations.

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Published on: August 15, 2018

Area of Science:

Environmental Science
Geochemistry
Microbiology

Background:

Nitrite (NO2-) is a key intermediate in nitrogen cycling, found in aquatic and terrestrial environments.
Accurate isotopic analysis of nitrite is essential for interpreting nitrogen cycling and correcting nitrate (NO3-) measurements.
Nitrite interferes with standard nitrate isotope analysis methods.

Purpose of the Study:

To adapt and validate the denitrifier method for oxygen isotope analysis of nitrite.
To investigate oxygen isotope fractionation during nitrite reduction.
To provide recommendations for sample storage and analysis of nitrite isotopes.

Main Methods:

Preparation and calibration of nitrite salts with varying oxygen isotopic compositions.
Testing the denitrifier method using Pseudomonas aureofaciens for nitrite reduction to nitrous oxide (N2O).
Evaluation of oxygen isotope exchange between nitrite and water.

Main Results:

Oxygen isotopic fractionation during nitrite reduction to N2O is lower than for nitrate.
Oxygen isotope exchange between nitrite and water during reduction is similar to nitrate.
The denitrifier method is extended for nitrite oxygen isotope analysis in nitrate-free samples.
Recommendations for sample storage conditions were established.

Conclusions:

The denitrifier method can be reliably used for oxygen isotope analysis of nitrite.
Accurate nitrite isotope measurements are vital for understanding nitrogen cycling and correcting nitrate isotope data.
Equilibrium isotope effects between nitrite and water are significant in determining nitrite's oxygen isotopic value.