EST | 全球农业系统中氮沉降引发的土壤N2O排放
文献信息：
Yang Yuyu, Liu Lei*, Zhang Feng, Zhang Xiuying, Xu Wen, Liu Xuejun, Wang Zhen, Xie Yaowen*. Soil nitrousoxide emissions by atmospheric nitrogen deposition over global agricultural systems[J]. Environmental Science & Technology, 2021. DOI: 10.1021/acs.est.0c08004
Environmental Science & Technology最新影响因子：7.864
摘 要：农业土壤是氧化亚氮（N2O）排放的主要来源，导致全球变暖和平流层臭氧消耗。近几十年来，大气氮沉降作为一种重要的农业土壤氮输入急剧增加，但其对土壤N2O排放的影响在当前和未来气候变化中仍不清楚。本文对氮沉降和气候变化对土壤N2O排放的影响及其变化趋势进行了深入分析。氮沉降引起的土壤N2O排放量占全球农田土壤N2O排放量的25%。1996-2013年间，全球农田土壤N2O排放量以2% yr-1的速度增长，其中氮沉降可解释增量的15%。由于氮沉降包含的硝态氮（NO3-）和铵态氮（NH4+）可以直接用于硝化和反硝化作用，因此通过更直接的方式推算出氮沉降的排放因子是化学氮肥+有机肥排放因子（~1%）的7倍。到2100年，在RCP8.5情景下，与2010年基线相比，氮沉降量将增加80%，而农田土壤N2O排放量将增加241%。这些结果表明，在全球氮沉降增加的背景下，在气候变化研究中必须考虑氮沉降对土壤N2O排放的影响。
Abstract: Agricultural soil is the main source of nitrous oxide (N2O) emissions which contribute to global warming and stratospheric ozone depletion. In recent decades, atmospheric nitrogen (N) deposition has increased dramatically as an important agricultural soil N input, while its effect on soil N2O emissions in the current and future climate change remains unknown. Here, we conducted a thorough analysis of the effect of N deposition and climate change on soil N2O emissions as well as their trends. Soil N2O emissions induced by N deposition accounted for 25% of global cropland soil N2O emissions. Global soil N2O emissions over croplands increased by 2% yr–1 during 1996–2013, of which N deposition could explain 15% of the increase. The emission factor of N deposition was ∼7 times that of N fertilizer plus manure (∼1%) through a more direct way, since N deposition including nitrate (NO3–) and ammonium (NH4+) could be directly used for nitrification and denitrification. By 2100, N deposition will increase by 80% and cropland soil N2O emissions will increase by 241% under the RCP8.5 scenario in comparison with the 2010 baseline. These results suggest that, under the background of increasing global N deposition, it is essential to consider its effects on soil N2O emissions in climatic change studies.
Graphical abstract:
Figure 1. Soil N inputs: (a) spatial map of cropland soil N inputs; (b) contribution of each factor to soil N inputs (left) and summary of soil N inputs in hotspot regions (right); (c) temporal changes of soil N inputs.
Figure 2. Soil N2O emissions and trends during 1996–2013: (a) spatial map of cropland soil N2O emissions averaged from 1996 to 2013; (b) gridded soil N2O emissions induced by N deposition; (c) annual changes in soil N2O emissions across the globe and in hotspot regions; (d) Contribution of each N input to soil N2O emissions, including N deposition, N fertilizer plus manure, and crop residues plus fixation, in hotspot regions.
Figure 3. Global croplands soil N2O emissions in different soil N input factors: (a) contributions of each factor to soil N2O emissions during 1996–2013 including N fixation, crop residues, N deposition, N manure, and N fertilizer; (b) temporal changes in N2O emissions induced by different N input factors.
Figure 4. Temporal changes of N2O emission factors among different soil N inputs during 1996–2013, including N fertilizer, manure amendment, N deposition, crop residues, and N fixation.
Figure 5. Cropland soil N2O emissions in future scenarios (RCP4.5 and RCP8.5): (a) soil N2O emissions under RCP4.5 and RCP8.5; (b) soil N2O emissions induced by N deposition under RCP4.5 and RCP8.5; (c, d) contributions of each factor to soil N2O emissions under (c) RCP4.5 and (d) RCP8.5.
Figure 6. Schematic illustration of N deposition for generating N2O in agricultural systems on the basis of RCP4.5. The trend of N deposition, precipitation, and temperature was based on the RCP 4.5 scenario. The trend of soil N2O emissions induced by N deposition is 0.9% N yr–1 under the RCP4.5 scenario.
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