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| Year-round measurements of nitric oxide emissions from a typical forage grass cropland in the QinghaiTibetan Plateau, China |
| Received:April 02, 2018 Revised:June 27, 2018 |
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| KeyWord:nitric oxide;soil freeze-thaw;sensitivity coefficient of temperature;direct emission factor;oat |
| Author Name | Affiliation | E-mail | | LIN Fei | State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | LIU Chun-yan | State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China | lcy@post.iap.ac.cn | | HU Xiao-xia | State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | FU Yong-feng | State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | ZHANG Wei | State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China | | | WANG Rui | State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China | | | YAO Zhi-sheng | State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China | | | ZHENG Xun-hua | State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
University of Chinese Academy of Sciences, Beijing 100049, China | |
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| Abstract: |
| Fertilized soils are major sources of atmospheric nitric oxide (NO). However, year-round measurements of NO emissions from croplands are still scarce and exclusively concentrated in the temperate and subtropical monsoon regions of China. In this study, yearround measurements of NO fluxes and environmental factors were conducted in a typical forage grass (oat)cropland in the Qinghai-Tibetan Plateau, which has a plateau climate. The annual NO emissions from the fertilized (F)and unfertilized (UF)treatments were 0.80±0.06 kg N·hm-2·a-1 and 0.18 ±0.04 kg N·hm-2·a-1, respectively. The cumulative emissions from the tillage-fertilization and freeze-thaw periods dominated the annual totals. The fitting equations between environmental factors and NO fluxes well characterized the integrated effects of substrate availability, oxidation-reduction condition, and microbial activity on NO emissions (r2=0.92). The sensitivity coefficients of NO emissions on soil temperatures (Q10)were 2.4 (F)and 2.5 (UF). The low Q10 values indicated that the enhanced effects of global warming on NO emissions were much lower than the promoted effects of fertilization on the emissions. The direct emission factor (EFd)was calculated as 0.93%±0.10% in the alpine oat field, which was higher than that of the regional, national, and global averages. Thus, the default EFd provided by other studies should not be applied to estimate NO emissions from croplands in a plateau climate. Considering the huge variation of precipitation across the plateau, multi-year continuous measurements are essential for quantifying the interannual variations of cumulative emissions and EFd. |
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