Identifying Ammonia Hotspots in China Using a National Observation Network

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Air Pollution Studies

Background:

• Limited ammonia (NH3) measurements hinder understanding of its role in secondary aerosol formation and reactive nitrogen deposition.
• Haze pollution events are exacerbated by NH3, necessitating better data for effective mitigation strategies.

Purpose of the Study:

• To investigate the national-scale spatial distributions and seasonal variations of atmospheric NH3 in China.
• To address observational gaps in NH3 measurements and their impact on air quality assessments.

Main Methods:

• A 1-year observational campaign was conducted at 53 uniform sites across China.
• Measurements were compared with satellite column concentrations and a bottom-up agriculture NH3 emission inventory.

Main Results:

• Abundant NH3 concentrations (1-23.9 μg m-3) were found in agricultural regions, especially the North China Plain.
• Urban and desert site NH3 levels were comparable to agricultural sites, and 2-3 times higher than natural environments.
• NH3 deposition fluxes in urban areas were half of NCP emissions, indicating significant downwind transport.

Conclusions:

• Spatial patterns of NH3 align with satellite data and agricultural emissions, but urban and desert sites show unexpectedly high concentrations.
• Urban NH3 emissions are transported to downwind areas, suggesting nonagricultural sources are critical for pollution control.
• Findings offer insights for policymakers on mitigating NH3 pollution from developed regions.