Soil denitrification potential and its influence on N2O reduction and N2O isotopomer ratios. (1st October 2013)

• Record Type: Journal Article
• Authors: Köster, Jan Reent; Well, Reinhard; Dittert, Klaus; Giesemann, Anette; Lewicka‐Szczebak, Dominika; Mühling, Karl‐Hermann; Herrmann, Antje; Lammel, Joachim; Senbayram, Mehmet
• Is Part Of: Rapid communications in mass spectrometry. Volume 27:Number 21(2013)
• Page Start: 2363
• Page End: 2373
• Publication Date: 2013-10-01
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.6699
• Languages: English
• ISSNs: 0951-4198

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="rcm6699-sec-0001" sec-type="section"> <title>RATIONALE</title> <p>N<sub>2</sub>O isotopomer ratios may provide a useful tool for studying N<sub>2</sub>O source processes in soils and may also help estimating N<sub>2</sub>O reduction to N<sub>2</sub>. However, remaining uncertainties about different processes and their characteristic isotope effects still hamper its application. We conducted two laboratory incubation experiments (i) to compare the denitrification potential and N<sub>2</sub>O/(N<sub>2</sub>O+N<sub>2</sub>) product ratio of denitrification of various soil types from Northern Germany, and (ii) to investigate the effect of N<sub>2</sub>O reduction on the intramolecular <sup>15</sup>N distribution of emitted N<sub>2</sub>O.</p> </sec> <sec id="rcm6699-sec-0002" sec-type="section"> <title>METHODS</title> <p>Three contrasting soils (clay, loamy, and sandy soil) were amended with nitrate solution and incubated under N<sub>2</sub>‐free He atmosphere in a fully automated incubation system over 9 or 28 days in two experiments. N<sub>2</sub>O, N<sub>2</sub>, and CO<sub>2</sub> release was quantified by online gas chromatography. In addition, the N<sub>2</sub>O isotopomer ratios were determined by isotope‐ratio mass spectrometry (IRMS) and the net enrichment factors of the <sup>15</sup>N site preference (SP) of the N<sub>2</sub>O‐to‐N<sub>2</sub> reduction step (η<sub>SP</sub>) were estimated using a Rayleigh model.</p> </sec> <sec id="rcm6699-sec-0003" sec-type="section"> <title>RESULTS</title> <p>The total denitrification rate was highest in clay soil and lowest in sandy soil. Surprisingly, the N<sub>2</sub>O/(N<sub>2</sub>O+N<sub>2</sub>) product ratio in clay and loam soil was identical; however, it was significantly lower in sandy soil. The IRMS measurements revealed highest N<sub>2</sub>O SP values in clay soil and lowest SP values in sandy soil. The <italic>η</italic><sub>SP</sub> values of N<sub>2</sub>O reduction were between –8.2 and –6.1 ‰, and a significant relationship between δ<sup>18</sup>O and SP values was found.</p> </sec> <sec id="rcm6699-sec-0004" sec-type="section"> <title>CONCLUSIONS</title> <p>Both experiments showed that the N<sub>2</sub>O/(N<sub>2</sub>O+N<sub>2</sub>) product ratio of denitrification is not solely controlled by the available carbon content of the soil or by the denitrification rate. Differences in N<sub>2</sub>O SP values could not be explained by variations in N<sub>2</sub>O reduction between soils, but rather originate from other processes involved in denitrification. The linear δ<sup>18</sup>O vs SP relationship may be indicative for N<sub>2</sub>O reduction; however, it deviates significantly from the findings of previous studies. Copyright © 2013 John Wiley & Sons, Ltd.</p> </sec> </abstract>