title: Re-estimating NH3 Emissions from Chinese Cropland by a New Nonlinear Model.
abstract: Ammonia (NH3) released to the atmosphere leads to a cascade of impacts on the environment, yet estimation of NH3 volatilization from cropland soils (VNH3) in a broad spatial scale is still quite uncertain in China. This mainly stems from nonlinear relationships between VNH3 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 VNH3 to nitrogen application rates (Nrate) (VR, %). The VNH3-Nrate relationship was nonlinear. The VR of upland soils and paddy soils depended primarily on local water input and Nrate, respectively. Our model demonstrated good reproductions of VNH3 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 VNH3 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.
authors.affiliation: Institute of Integrated Watershed Management, Sino-France Institute of Earth Systems Science, Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University , Beijing, 100871, P.R. China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhou
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, CEA CNRS UVSQ , 91191 Gif-sur-Yvette, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Ciais
authors.affiliation: Carbon and Nutrient Cycles Division, National Institute for Agro-Environmental Sciences , 3-1-3, Kannondai, Tsukuba, Ibaraki 305-8604, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Hayashi
authors.affiliation: Environmental Sciences Department, University of Virginia , Charlottesville, Virginia 22904, United States.
authors.forename: James
authors.initials: J
authors.lastname: Galloway
authors.affiliation: Wondo Genet College of Forestry and Natural Resources, Hawassa University , Shashemene, Ethiopia.
authors.forename: Dong-Gill
authors.initials: DG
authors.lastname: Kim
authors.affiliation: Research Institute of Engineering Technology, Yunnan University , Kunming, 650091, P.R. China.
authors.forename: Changliang
authors.initials: C
authors.lastname: Yang
authors.affiliation: Research Institute of Engineering Technology, Yunnan University , Kunming, 650091, P.R. China.
authors.forename: Shiyu
authors.initials: S
authors.lastname: Li
authors.affiliation: Research Institute of Engineering Technology, Yunnan University , Kunming, 650091, P.R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.affiliation: Institute of Integrated Watershed Management, Sino-France Institute of Earth Systems Science, Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University , Beijing, 100871, P.R. China.
authors.forename: Ziyin
authors.initials: Z
authors.lastname: Shang
authors.affiliation: Institute of Integrated Watershed Management, Sino-France Institute of Earth Systems Science, Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University , Beijing, 100871, P.R. China.
authors.forename: Shuoshuo
authors.initials: S
authors.lastname: Gao
mesh_terms: D000393:Air Pollutants / Q000378:metabolism*; D000641:Ammonia / Q000378:metabolism*; D002681:China; D018556:Crops, Agricultural / Q000378:metabolism*; D004784:Environmental Monitoring; D008954:Models, Biological; D017711:Nonlinear Dynamics
chemical_list: D000393:Air Pollutants; D000641:Ammonia