Rainwater, soil water, and soil nitrate effects on oxygen isotope ratios of nitrous oxide produced in a green tea (Camellia sinensis) field in Japan. (30th March 2015)

• Record Type: Journal Article
• Authors: Zou, Yun; Hirono, Yuhei; Yanai, Yosuke; Hattori, Shohei; Toyoda, Sakae; Yoshida, Naohiro
• Is Part Of: Rapid communications in mass spectrometry. Volume 29:Number 9(2015)
• Page Start: 891
• Page End: 900
• Publication Date: 2015-03-30
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.7176
• Languages: English
• ISSNs: 0951-4198

Abstract

Abstract : Rationale: The oxygen exchange fraction between soil H2 O and N2 O precursors differs in soils depending on the responsible N2 O‐producing process: nitrification or denitrification. This study investigated the O‐exchange between soil H2 O and N2 O precursors in a green tea field with high N2 O emissions. Methods: The rainwater δ 18 O value was measured using cavity ring‐down spectrometry (CRDS) and compared with that of soil water collected under the tea plant canopy and between tea plant rows. The intramolecular 15 N site preference in β N α NO (SP = δ 15 N α – δ 15 N β ) was determined after measuring the δ 15 N α and δ 15 N bulk values using gas chromatography/isotope ratio mass spectrometry (GC/IRMS), and the δ 18 O values of N2 O and NO3 – were also measured using GC/IRMS. Results: The range of δ 18 O values of rainwater (–11.15‰ to –4.91‰) was wider than that of soil water (–7.94‰ to –5.64‰). The δ 18 O value of soil water at 50 cm depth was not immediately affected by rainwater. At 10 cm and 20 cm depths of soil between tea plant rows, linear regression analyses of δ 18 O‐N2 O (relative to δ 18 O‐NO3 – ) versus δ 18 O‐H2 O (relative to δ 18 O‐NO3 – ) yielded slopes of 0.76–0.80 and intercepts of 31–35‰. Conclusions: In soil between tea plant rows, the fraction of O‐exchange between H2 O and N2 O precursors was approximately 80%. Assuming that denitrification dominated N2 O production, the net 18 O‐isotope effect for denitrification (NO3 – reduction to N2 O) was approximately 31–35‰, reflecting the upland condition of the tea field. Copyright © 2015 John Wiley & Sons, Ltd.