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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-749
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
17 Aug 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
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, and Binxiang Huang8 1Laboratory for Climate and Ocean-Atmosphere Sciences, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China
2Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309, USA
3Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, 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, New Jersey 08540, 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
8Department 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 11.7 Tg for 2008 with 5.05 Tg from fertilizer application and 5.31 Tg 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 well reproduces the observed spatial and seasonal variations of NH3 gas concentrations and ammonium (NH4+) wet deposition fluxes over China, providing additional credibility to the improvements we have made to our agricultural NH3 emission inventory.

Citation: Zhang, L., Chen, Y., Zhao, Y., Henze, D. K., Zhu, L., Song, Y., Paulot, F., Liu, X., Pan, Y., and Huang, B.: Agricultural ammonia emissions in China: reconciling bottom-up and top-down estimates, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-749, in review, 2017.
Lin Zhang et al.
Lin Zhang et al.

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Short summary
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 teragram for 2008 with a strong seasonality peaking in summer.
Substantial differences exist in current estimates of agricultural ammonia emissions in China,...
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