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δ 15 N of Nitric Oxide Produced Under Aerobic or Anaerobic Conditions From Seven Soils and Their Associated N Isotope Fractionations
Author(s) -
Su Chenxia,
Kang Ronghua,
Zhu Weixing,
Huang Wentao,
Song Linlin,
Wang Ang,
Liu Dongwei,
Quan Zhi,
Zhu Feifei,
Fu Pingqing,
Fang Yunting
Publication year - 2020
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2020jg005705
Subject(s) - environmental chemistry , anaerobic exercise , soil water , nitrification , isotopes of nitrogen , denitrification , nitrous oxide , chemistry , nitrogen , fractionation , aerobic denitrification , ecosystem , environmental science , soil science , denitrifying bacteria , ecology , biology , physiology , organic chemistry
Measuring the nitrogen isotope compositions (δ 15 N) of nitric oxide (NO) from different sources helps to quantify the relative contributions of atmospheric NO x . Soil is one of the most important sources of atmospheric NO x , but only limited measurements on the δ 15 N of soil‐emitted NO exist, hampering our ability to partition sources to air pollution. Here we conducted soil incubations to measure the δ 15 N‐NO under defined aerobic or anaerobic conditions, favoring either nitrification or denitrification. Soils were collected from seven sites spanning three ecosystems in northern China (two agricultural, two forest, and three grassland sites). We found that the δ 15 N‐NO and their associated N isotope fractionations were significantly different between anaerobic and aerobic conditions in seven soils. Under aerobic condition, the δ 15 N‐NO ranged from −62‰ to −50‰ (averaged −56 ± 4‰), being significantly more negative (by 23‰) than those under anaerobic condition (−45‰ to −23‰, averaged −33 ± 7‰). The apparent N isotope fractionation for NO production under aerobic condition ( 15 ε aerobic = 61 ± 3‰) was significantly higher (by 26‰) than under anaerobic condition ( 15 ε anaerobic = 35 ± 6‰), with a small variability among ecosystem types. Our study demonstrates that the δ 15 N‐NO from different soils are very different from fuel combustions (mainly from 0‰ to +20‰), supporting that measuring 15 N is a useful tool to partition the contributions of soil NO to atmospheric NO x . Our results also imply δ 15 N‐NO produced by nitrification and denitrification distinctly different, as these two processes are dominant processes producing NO under aerobic and anaerobic conditions, respectively.