资源环境科技发展态势分析平台

The U.S. 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 U.S. National Emissions Inventory (NEI) and WRF‐Chem simulations to constrain NH3 emissions from April‐September, 2017‐2019. We show that: (1) NH3 emissions peaked from May to July and were 1.6 to 1.7 times the annual NEI average; (2) average growing season NH3 emissions from agricultural lands were remarkably similar across years (3.27 to 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.