Quantifying the Impact of Agricultural Ammonia Increases on Particulate Matter Burden over the Midwestern United States
TOAN VO, Amy Christiansen,
University of Missouri - Kansas City Abstract Number: 683
Working Group: Aerosol Chemistry
AbstractOver the past few decades, ammonia (NH
3) emissions have strongly increased in the highly agricultural Midwestern United States (MWUS). Ammonia serves as a key precursor species in the formation of fine particulate matter (PM
2.5), which impacts human health and Earth’s climate. However, NH
3 emissions are not regulated at the federal level, and the impacts of agricultural NH
3 to air quality in urban areas are not well quantified. The goal of this work is to determine the impact of increasing agricultural NH
3 on nitrogen deposition and the formation and chemical composition of PM
2.5 from 2007 to 2019 through GEOS-Chem model simulations and observational data from the Ammonia Monitoring Network (AMoN), Clean Air Status and Trends Network (CASTNET), and the Interagency Monitoring of Protected Visual Environments (IMPROVE) throughout the MWUS. We find significant increases in NH
3 of >50% on average across the MWUS region for all seasons, especially during winter, where most of the sites in the MWUS exhibit > 100% increases. Wet deposition of NH
4+ increases by>75% during summer, fall, and winter. Additionally, the contribution of NH
4+ to total nitrogen deposition increased from 35% in 2007 to >50% in 2019. Although overall PM
2.5 concentrations have decreased by >50%, NH
4+ makes up >50% of the particle mass in the MWUS, which is on average 25% higher than in the rest of the United States, indicating ammonia emissions are a contributing factor to changes in particle chemical composition. Finally, we discuss the impact of increasing agricultural NH
3 on PM
2.5 in the MWUS and downwind areas using sensitivity simulations in the chemical transport model GEOS-Chem, and we quantify the PM
2.5 burden attributable to agricultural NH
3. Overall, this work joins the growing body of literature suggesting NH
3 emissions should be regulated federally to reduce PM
2.5 formation and protect public health.
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