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Direct Measurement of Dinitrogen Evolution from Soil Using Nitrogen‐15 Emission Spectrometry
Author(s) -
Kjeldby M.,
Eriksen A. B.,
HoltanHartwig L.
Publication year - 1987
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1987.03615995005100050016x
Subject(s) - cuvette , nitrogen , chemistry , analytical chemistry (journal) , mass spectrometry , isotope , fertilizer , atmosphere (unit) , environmental chemistry , chromatography , organic chemistry , physics , quantum mechanics , thermodynamics
When a 15 N‐enriched N source is added to the soil, denitrification results in a nonrandom distribution of N 2 isotopes. As a result, it has been necessary to apply highly enriched 15 N‐fertilizers to allow mass spectrometry (MS) determinations of 28 N 2 , 29 N 2 , and 30 N 2 to quantify the N 2 evolution. An alternative method, based on the determination of N 2 evolution by measurement of the 28 N 2 / 29 N 2 ratio with emission spectrometry (ES), is proposed. An apparatus consisting of a cuvette and a sampling system was developed. The sampling system was evacuated to <10 −1 Pa before gas from the cuvette system was fed into a reservoir (10 mL), through a liquid N 2 trap and into five discharge tubes for ES. The final pressure in the tubes was 4 to 5 × 10 2 Pa before they were sealed off, and the 28 N 2 / 29 N 2 ratios in the gases were determined with ES. It was verified that random distribution of 28 N 2 , 29 N 2 , and 30 N 2 was obtained in different N 2 ‐gas mixtures made from natural atmosphere and 98 atom % 15 N‐N 2 by the high frequency discharge of the ES. The system was used to measure fertilizer N 2 loss when 15 N‐enriched KNO 3 was applied at a depth of 2.5 cm in flooded soil. After 60 d, 18% of the applied KNO 3 was lost as N 2 .