Environmental impact of atmospheric NH3 emissions under present and future conditions in the eastern United States

Recent regulations require large‐scale emission reductions of NOx and SO2 in the eastern United States. These emission changes will alter the partitioning of ammonia between the gas and particle phases. Furthermore, ammonia emissions are expected to increase in the future. How will these changes impact the contribution of ammonia to inorganic particulate matter and nitrogen deposition? We use a chemical transport model and emission scenarios representing years 2001, 2010, and 2020 to estimate the future change of the sensitivity of iPM2.5 to ammonia emission reductions and change in nitrogen deposition to ecosystems. We find that during winter conditions, particulate matter concentrations in several locations in the Midwestern US continue to have significant sensitivity to NH3 emissions. In addition, the total nitrogen deposition near NH3 emission sources increases 10–40%