Date of Award
5-11-2025
Date Published
June 2025
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Civil and Environmental Engineering
Advisor(s)
Charley Driscoll
Keywords
air quality;Decarbonization;Environmental benefits;machine learning;tree growth;tree survival
Subject Categories
Civil and Environmental Engineering | Engineering | Environmental Engineering
Abstract
In the United States, power generation significantly contributes to emissions of sulfur dioxide and nitrogen oxides, two precursors to atmospheric reactive nitrogen and sulfur deposition. In this thesis, I explore the prospective changes associated with the decarbonization of the electricity sector in atmospheric emissions and deposition of nitrogen oxides (NOx), sulfur oxides (SOx), and ammonia (NH3), and the implications of these alterations for shifts in patterns of interstate air pollutant transport and exceedances of critical loads of nitrogen and sulfur deposition impacting the growth and mortality of tree species in the coterminous U.S. While existing research provides some understanding of potential improvements in air quality and health benefits through reductions in atmospheric emissions, few studies have investigated the future changes in atmospheric deposition, and critical load exceedances in relation to ecosystem benefits. In this study, the Integrated Planning Model (IPM) is utilized to forecast emission changes of key deposition pollutants under different decarbonization policy scenarios for 2020 to 2050. These emission forecasts serve as inputs for the Community Multiscale Air Quality Model (CMAQ), which is used to compute changes in atmospheric deposition of nitrate, sulfate, and ammonium/ammonia for the policies considered. Subsequently, projected deposition values are used to assess changes in interstate transport of air pollutants and exceedances in critical loads of nitrogen and sulfur, crucial for the growth and survival of tree species across the conterminous U.S. I found that high-ambition decarbonization policies can lead to meaningful reductions in national average total sulfur deposition (-0.25 to -0.30 kg-S ha-1yr-1) by 2040, with less for total nitrogen (-0.09 to -0.12 kg-N ha-1yr-1). While deposition reductions are projected for all states, the most significant decreases in comparison to a business-as-usual (BAU) scenario - nearly 20% for NO3- and 50% for SO42- - occur in the eastern U.S, specifically in the Mid-West, Eastern Seaboard, and Texas. Such policies also mitigate transboundary emission impacts, fostering greater equity for lower-polluting states like Michigan, New York, and Vermont. Lastly, hypothetical air quality controls related to these policies would yield substantial ecological benefits, primarily through sulfur reductions. The land area where over 20% of tree species exceed the sulfur critical loads to protect growth is projected to decrease from 9.9% under a business-as-usual scenario to 7.1% under an aggressive decarbonization policy (CES40B) in 2040. Similarly, the area of critical load exceedance for tree survival decreases from 15.1% to 13.6%. Smaller decreases in exceedances of critical loads of nitrogen deposition for tree growth and survival are anticipated due to the lower projected reductions.
Access
Open Access
Recommended Citation
Mehdi, Qasim, "Assessing changes in emissions and atmospheric deposition of sulfur dioxide and nitrogen oxides under policies to decarbonize the electricity sector in the US" (2025). Theses - ALL. 919.
https://surface.syr.edu/thesis/919
