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Volume 18, issue 1 | Copyright

Special issue: Regional transport and transformation of air pollution in...

Atmos. Chem. Phys., 18, 339-355, 2018
https://doi.org/10.5194/acp-18-339-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 12 Jan 2018

Research article | 12 Jan 2018

Agricultural ammonia emissions in China: reconciling bottom-up and top-down estimates

Lin Zhang1, Youfan Chen1, Yuanhong Zhao1, Daven K. Henze2, Liye Zhu3, Yu Song4, Fabien Paulot5, Xuejun Liu6, Yuepeng Pan7, Yi Lin8, and Binxiang Huang9 Lin Zhang et al.
  • 1Laboratory for Climate and Ocean–Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China
  • 2Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309, USA
  • 3Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095, USA
  • 4State Key Joint Laboratory of Environmental Simulation and Pollution Control, Department of Environmental Science, Peking University, Beijing 100871, China
  • 5Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ 08544, USA
  • 6Key Laboratory of Plant–Soil Interactions of MOE, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100094, China
  • 7State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 8School of Earth and Space Sciences, Peking University, Beijing 100871, China
  • 9Department of Agrometeorology, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China

Abstract. Current estimates of agricultural ammonia (NH3) emissions in China differ by more than a factor of 2, hindering our understanding of their environmental consequences. Here we apply both bottom-up statistical and top-down inversion methods to quantify NH3 emissions from agriculture in China for the year 2008. We first assimilate satellite observations of NH3 column concentration from the Tropospheric Emission Spectrometer (TES) using the GEOS-Chem adjoint model to optimize Chinese anthropogenic NH3 emissions at the 1∕2° × 2∕3° horizontal resolution for March–October 2008. Optimized emissions show a strong summer peak, with emissions about 50% higher in summer than spring and fall, which is underestimated in current bottom-up NH3 emission estimates. To reconcile the latter with the top-down results, we revisit the processes of agricultural NH3 emissions and develop an improved bottom-up inventory of Chinese NH3 emissions from fertilizer application and livestock waste at the 1∕2° × 2∕3° resolution. Our bottom-up emission inventory includes more detailed information on crop-specific fertilizer application practices and better accounts for meteorological modulation of NH3 emission factors in China. We find that annual anthropogenic NH3 emissions are 11.7Tg for 2008, with 5.05Tg from fertilizer application and 5.31Tg from livestock waste. The two sources together account for 88% of total anthropogenic NH3 emissions in China. Our bottom-up emission estimates also show a distinct seasonality peaking in summer, consistent with top-down results from the satellite-based inversion. Further evaluations using surface network measurements show that the model driven by our bottom-up emissions reproduces the observed spatial and seasonal variations of NH3 gas concentrations and ammonium (NH4+) wet deposition fluxes over China well, providing additional credibility to the improvements we have made to our agricultural NH3 emission inventory.

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Substantial differences exist in current estimates of agricultural ammonia emissions in China, hindering understanding of their environmental consequences. This study applies both bottom-up and top-down methods to better quantify agricultural ammonia sources in China using observations from satellite and surface networks interpreted by a chemical transport model. Our estimate of annual Chinese anthropogenic ammonia emission is 11.7 tg (teragram) for 2008 with a strong seasonality peak in summer.
Substantial differences exist in current estimates of agricultural ammonia emissions in China,...
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