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Trends in U.S. ammonia emissions and lifetime
Citation:
Baublitz, C., V. Rao, B. Henderson, K. Seltzer, L. Dayton, J. Bash, Y. Dietrich, A. Eyth, J. Mangino, K. Foley, AND C. Hogrefe. Trends in U.S. ammonia emissions and lifetime. The 105th American Meteorological Society Annual Meeting, New Orleans, LA, January 12 - 16, 2025.
Impact/Purpose:
This presentation will document the change in the composition of atmospheric pollutants and document how gaseous NH3 levels have changed with emissions and how the reduction of NO2 and SO2 have changed its atmospheric transport and deposition. Emission sector information and how it has changed over this time period will be discussed with an emphasis on how to better develop future national emission inventories that improve the representation of NH3 emission sources.
Description:
Gaseous ammonia (NH3) is the primary alkaline gas in the atmosphere. It contributes to ambient fine particulate matter formation, and its adverse health effects, by combining with acidic gases such as sulfuric and nitric acid. NH3 is directly emitted, is not formed by photochemical reactions, and has become the primary contributor to reactive nitrogen deposition over most of the USA. Via deposition, NH3 also degrades ecosystems. Unlike the decreasing trend seen in other PM2.5 precursor emissions over the last 20 years, NH3 emissions in the United States have increased by approximately 20%. The corresponding change in PM2.5 sensitivity to precursor gases has also affected the residence time of NH3 and therefore the extent of its influence on ecosystems via deposition. Here, we illustrate the relative contributions of NH3 sources to total NH3 emissions, as reported in the U.S. Environmental Protection Agency’s (EPA) National Emissions Inventory (NEI). This includes agricultural sources (livestock waste and fertilizer application) and increasingly acknowledged contributions from onroad mobile sources and fires. We briefly outline the bottom-up estimation methods for NH3 emissions from some of these sources in the NEI, show their relative emission magnitudes in the 2020 NEI, illustrate sector-based emission trends over time, and point to future work to be done to improve current methods and add missing sources of NH3 to the NEI. We will also use the EPA’s Air Quality Time Series (EQUATES) dataset, which provides 18 years of consistently configured regional chemical transport model (CMAQ) simulations, to explore spatiotemporal trends in NH3 loss pathways.
URLs/Downloads:
https://www.ametsoc.org/index.cfm/ams/meetings-events/upcoming-meetings/annual-meeting/