A Multiyear Constraint on Ammonia Emissions and Deposition Within the US Corn Belt

Cheng Hu, Timothy J. Griffis, Alexander Frie, John M. Baker, Jeffrey D. Wood, Dylan B. Millet, Zhongjie Yu, Xueying Yu, Alan C. Czarnetzki

Research output: Contribution to journalArticlepeer-review


The US Corn Belt is a global hotspot of atmospheric ammonia (NH3), a gas known to adversely impact the environment and human health. We combine hourly tall tower (100 m) measurements and bi-weekly, spatially distributed, ground-based observations from the Ammonia Monitoring Network with the US National Emissions Inventory (NEI) and WRF-Chem simulations to constrain NH3 emissions from April to September 2017–2019. We show that: (1) NH3 emissions peaked from May to July and were 1.6–1.7 times the annual NEI average; (2) average growing season NH3 emissions from agricultural lands were remarkably similar across years (3.27–3.64 nmol m−2 s−1), yet showed substantial episodic variability driven by meteorology and land management; (3) dry deposition was 40% of gross emissions from agricultural lands and exceeded 100% of gross emissions in natural lands. Our findings provide an important benchmark for evaluating future NH3 emissions and mitigation efforts.

Original languageEnglish (US)
Article numbere2020GL090865
JournalGeophysical Research Letters
Issue number6
StatePublished - Mar 28 2021
Externally publishedYes


  • US Corn Belt
  • WRF-Chem modeling
  • agriculture
  • ammonia emissions
  • deposition
  • forests
  • mitigation
  • reactive nitrogen
  • tall tower

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)


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