Semester of Graduation

Summer 2019

Degree

Master of Science in Civil Engineering (MSCE)

Department

Civil and Environmental Engineering (CEE)

Document Type

Thesis

Abstract

Nitrogen (N) and sulfur (S) are essential nutrients, however excess quantities can stress ecosystems. Atmospheric nitrogen and sulfur deposition lead to changes in water and soil chemistry, consequently resulting in ensuing detriment to multiple ecosystems such as acidification of water bodies. This affects a multitude of plants and animals such as trees, insects, and fish. Louisiana has copious natural water resources. Therefore, it is essential to safeguard its valuable resources from excess atmospheric N and S deposition. However, knowledge of N and S deposition and its unfavorable effects in the Southeast U.S., particularly Louisiana, is limited.

In this research, a source-oriented Community Multi-scale Air Quality (CMAQ) model was employed to simulate present and future emission, formation, transport, and deposition of S and N species in Louisiana for the purpose of understanding the forms and amount of S and N deposition resulting from dry and wet deposition, to illustrate the spatiotemporal alterations of deposition fluxes, and to quantitate the contributions of various sources to N and S deposition. The Weather Research and Forecasting (WRF) model was utilized to predict future variations in climate and the subsequent fluctuations of deposition due to climate change. The Sparse Matrix Operator Kernel Emissions (SMOKE) model was used to convert the resolution of the emission inventory data to the resolution required by CMAQ.

As predicted, nitrogen and sulfur deposition fluxes were lowest in the controlled case, followed by the no change case and business as usual case. However, although N and S deposition were lowest in the controlled emission scenario, there was still a significant increase of deposition fluxes.

The prevailing contributor of wet deposition of S was particulate sulfate (AeroSO4) with peak total monthly flux of 6 kg S/ha, whereas the chief form of dry deposition of S was SO2 with a total monthly flux of approximately 3 kg S/ha. Deposition of N was predominantly in the following forms: NH3, HNO3, NO2, and particulate nitrate (AeroNO3). Electric generating utilities (EGU), industry, and upwind sources were the three primary sources of sulfur deposition, with EGU contributing the most (1.6 kg S/ha per month) followed by industry (1 kg S/ha per month) and upwind sources. Industry (0.8 kg N/ha) and on-road vehicles (0.6 kg N/ha) were the leading source sectors of nitrogen deposition (excluding NH3). “Other” sources (containing agriculture) were the prevailing source of ammonia.

This research contributes to the understanding of N and S deposition and identifies key nitrogen and sulfur emission sources in Louisiana and is beneficial for the enhanced development of more effective nitrogen and sulfur emission regulation strategies. It pinpoints EGU, industry, and upwind sources as main S polluters and industry, on-road vehicles, and “other” sources (including agricultural sector) as principal N polluters. The results of this study will advise environmental policymakers on which sectors, species, and regions to target to better protect Louisiana’s valuable natural resources.

Committee Chair

Zhang, Hongliang

DOI

10.31390/gradschool_theses.4989

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