Effect of chloride on the chemical conversion of nitrate to nitrous oxide for δ15N analysis.

Ryabenko, Evgeniya, Altabet, Mark A. and Wallace, Douglas W.R. (2009) Effect of chloride on the chemical conversion of nitrate to nitrous oxide for δ15N analysis. Limnology and Oceanography: Methods, 7 . pp. 545-552. DOI 10.4319/lom.2009.7.545.

[img] Text
0545.pdf - Published Version
Restricted to Registered users only

Download (424Kb) | Contact

Supplementary data:


We investigate the influence of chloride concentration on the performance of the chemical reduction method for measurement of the nitrogen isotopic ratio (δ15N) in NO3− in natural waters (McIlvin and Altabet, 2005). In this method, NO3− is first reduced to NO2− using activated cadmium metal, with further reduction to N2O using sodium azide in an acetic acid buffer. N2O is introduced into an isotope ratio mass spectrometer (IRMS) for isotopic measurement. Previously, it was recognized that the presence of halides was necessary for the speed and efficiency of the second step but not thought to be important for the first step. Whereas quantitative Cd reduction of NO3− to NO2− had been noted for seawater samples, here we report, for freshwater and low‐salinity (S < 30) samples, a variable conversion efficiency (both under‐ and overreduction were observed) and significant variation in δ15N determination. Addition of 5 M NaCl to all samples resulted in rapid (<4 h) and quantitative (>99%) reduction of NO3− to NO2− as well as stable δ15N values that closely matched expected values for standards (within 0.3‰ of standard value). The positive effect of NaCl is likely due to a decrease in free Cd2+ produced over the course of the reaction due to formation of CdCl2.

Document Type: Article
Keywords: chloride, nitrogen isotopes
Research affiliation: OceanRep > SFB 754 > B4
OceanRep > SFB 754
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.4319/lom.2009.7.545
ISSN: 1541-5856
Projects: SFB754, Future Ocean
Date Deposited: 07 Dec 2009 13:50
Last Modified: 23 Sep 2019 19:35
URI: http://oceanrep.geomar.de/id/eprint/6254

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...