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| Dynamics of ammonia and ammonium at the atmosphere-vegetation interface over a selected maize farmland in the North China Plains |
| Received:December 12, 2017 |
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| KeyWord:ammonia;ammonium;vegetation canopy;farmland;maize leaf;atmospheric nitrogen deposition |
| Author Name | Affiliation | E-mail | | TIAN Shi-li | Institute of Atmospheric Physics, Chinese Academy of Sciences, LAPC, Beijing 100029, China | | | ZHU Xia-ying | National Climate Center, Beijing 100081, China | | | PAN Yue-peng | Institute of Atmospheric Physics, Chinese Academy of Sciences, LAPC, Beijing 100029, China | panyuepeng@mail.iap.ac.cn | | XIE Yu-zhu | Institute of Atmospheric Physics, Chinese Academy of Sciences, LAPC, Beijing 100029, China | | | ZHOU Yan-bo | Yangquan Meteorological Bureau, Yangquan 045000, China | | | ZHANG Guo-zhong | College of Forestry, Gansu Agricultural University, Lanzhou 730070, China | |
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| Abstract: |
| The exchange and variation of reduced nitrogen[gaseous ammonia (NH3) and particulate ammonium (NH4+), i.e., NHx] at the atmosphere-vegetation interface of a typical maize farmland ecosystem in north China were studied. Atmospheric concentrations of NH3 and NH4+ above the vegetation canopy, as well as NH4+ concentrations in maize leaves and soil samples, were simultaneously measured. The results showed that atmospheric concentrations of NH3 and NH4+ ranged from 21.1 to 37.6 μg·m-3 and from 2.1 to 8.0 μg·m-3, respectively. The removal efficiency of NH4+ (75%) by precipitation was much higher than that of NH3. The NH4+ content in maize leaves decreased from the top to the bottom of the maize plant, and tended to be higher as temperature increased. During the heading period, the average NH3 compensation point of leaves was 1.9±1.4 μg·m-3, which was lower than the canopy NH3 concentration (31.4±4.8 μg·m-3). Conversely, the average NH3 compensation point of leaves was 52.0±30.7 μg·m-3, which was higher than the canopy NH3 concentration (29.3±11.7 μg·m-3) during the anthesis maturity period. During the observation period between August 10 and 13, atmospheric reactive nitrogen deposition into the farmland via precipitation, gas, and aerosol was about 25 mg N·m-2·d-1, which was an important source of soil nitrogen and crop available nitrogen. The NH3 exchange between the atmosphere and plants should be considered in nitrogen management in intensive Chinese agricultural systems. |
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