A Bacterial Method for the Nitrogen Isotopic Analysis of Nitrate in Seawater and Freshwater

D. M. Sigman,*† K. L. Casciotti,† M. Andreani,‡ C. Barford,§ M. Galanter,† and J. K. Böhlke
Department of Geosciences, Guyot Hall, Princeton University, Princeton, New Jersey, 08544, Magistre de Sciences de la Terre, cole Normale Suprieure de Lyon, 46 Alle dItalie, Lyon, France 69364, Department of Earth and Atmospheric Sciences, Harvard University, Cambridge, MA 02138, and U.S. Geological Survey, 431 National Center, Reston, VA 20192
Anal. Chem., 2001, 73 (17), pp 4145–4153
DOI: 10.1021/ac010088e
Publication Date (Web): July 27, 2001
Copyright © 2001 American Chemical Society
*

 Corresponding author. Fax:  609-258-1274. E-mail:  sigman@princeton.edu.

,
†

 Princeton University.

,
‡

 École Normale Supérieure de Lyon.

,
§

 Harvard University.

,

 U.S. Geological Survey.

Abstract

We report a new method for measurement of the isotopic composition of nitrate (NO3-) at the natural-abundance level in both seawater and freshwater. The method is based on the isotopic analysis of nitrous oxide (N2O) generated from nitrate by denitrifying bacteria that lack N2O-reductase activity. The isotopic composition of both nitrogen and oxygen from nitrate are accessible in this way. In this first of two companion manuscripts, we describe the basic protocol and results for the nitrogen isotopes. The precision of the method is better than 0.2‰ (1 SD) at concentrations of nitrate down to 1 μM, and the nitrogen isotopic differences among various standards and samples are accurately reproduced. For samples with 1 μM nitrate or more, the blank of the method is less than 10% of the signal size, and various approaches may reduce it further.

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History

  • Published In Issue September 01, 2001
  • Received for review January 19, 2001. Accepted June 8, 2001.

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