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Rainwater, soil water, and soil nitrate effects on oxygen isotope ratios of nitrous oxide produced in a green tea ( Camellia sinensis ) field in Japan
Author(s) -
Zou Yun,
Hirono Yuhei,
Yanai Yosuke,
Hattori Shohei,
Toyoda Sakae,
Yoshida Naohiro
Publication year - 2015
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7176
Subject(s) - chemistry , camellia sinensis , nitrous oxide , environmental chemistry , nitrate , isotopes of oxygen , oxygen , nuclear chemistry , horticulture , biology , organic chemistry
Rationale The oxygen exchange fraction between soil H 2 O and N 2 O precursors differs in soils depending on the responsible N 2 O‐producing process: nitrification or denitrification. This study investigated the O‐exchange between soil H 2 O and N 2 O precursors in a green tea field with high N 2 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 N 2 O and NO 3 – 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‐N 2 O (relative to δ 18 O‐NO 3 – ) versus δ 18 O‐H 2 O (relative to δ 18 O‐NO 3 – ) 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 H 2 O and N 2 O precursors was approximately 80%. Assuming that denitrification dominated N 2 O production, the net 18 O‐isotope effect for denitrification (NO 3 – reduction to N 2 O) was approximately 31–35‰, reflecting the upland condition of the tea field. Copyright © 2015 John Wiley & Sons, Ltd.