Re-estimating NH3 Emissions from Chinese Cropland by a New Nonlinear Model

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• 作者：Feng Zhou ; Philippe Ciais ; Kentaro Hayashi ; James Galloway ; Dong-Gill Kim ; Changliang Yang ; Shiyu Li ; Bin Liu ; Ziyin Shang ; Shuoshuo Gao
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：January 19, 2016
• 年：2016
• 卷：50
• 期：2
• 页码：564-572
• 全文大小：557K
• ISSN：1520-5851

文摘

Ammonia (NH₃) released to the atmosphere leads to a cascade of impacts on the environment, yet estimation of NH₃ volatilization from cropland soils (V_NH3) in a broad spatial scale is still quite uncertain in China. This mainly stems from nonlinear relationships between V_NH3 and relevant factors. On the basis of 495 site-years of measurements at 78 sites across Chinese croplands, we developed a nonlinear Bayesian tree regression model to determine how environmental factors modulate the local derivative of V_NH3 to nitrogen application rates (N_rate) (VR, %). The V_NH3–N_rate relationship was nonlinear. The VR of upland soils and paddy soils depended primarily on local water input and N_rate, respectively. Our model demonstrated good reproductions of V_NH3 compared to previous models, i.e., more than 91% of the observed VR variance at sites in China and 79% of those at validation sites outside China. The observed spatial pattern of V_NH3 in China agreed well with satellite-based estimates of NH₃ column concentrations. The average VRs in China derived from our model were 14.8 ± 2.9% and 11.8 ± 2.0% for upland soils and paddy soils, respectively. The estimated annual NH₃ emission in China (3.96 ± 0.76 TgNH₃·yr^–1) was 40% greater than that based on the IPCC Tier 1 guideline.