Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- All Subjects: Environmental engineering
- Creators: Myint, Soe W.
Description
Approximately 71% of the great lakes, lakes, reservoirs, and ponds, together with 51% of rivers and streams assessed in the US are impaired or threatened by pollution or do not meet the minimum water quality requirements. Pathogens, sediments, and nutrients are leading causes of impairment, with agriculture being a top source of pollution. Agricultural pollution has become a global concern overtaking urban contamination as the major factor of inland and coastal waters degradation in many parts of the world. High-yielding crop production has been achieved by the intensive use of inorganic fertilizers that are mainly composed of Nitrogen (N) and Phosphorus (P). N and P are essential nutrients for ecosystem structure, processes, and functions. However, N and P in excess can be problematic to the environment. One of the major impacts of the increasing amount of these nutrients in the environment is the global expansion of harmful algal blooms (HABs). Major agricultural nutrient pollution sources and climate change can exacerbate these risks. This dissertation aims to guide future policies to mitigate issues linked to excess nutrient loads in the U.S. by evaluating the impact of climate change on nutrient loads and assessing the environmental impact as well as the spatial patterns of one of the major agricultural sources of nutrient pollution - Concentrated Animal Feeding Operations (CAFOs). Specifically, I first investigated the impact of bias correction techniques when modeling mid-century nutrient loads in a watershed heavily impacted by CAFOs. Second, I evaluated the role of CAFOs in land use change and subsequent environmental degradation of the surrounding environment. Finally, I assessed the spatial organization of CAFOs and its links to water quality conditions. The findings revealed unique insights for future nutrient management strategies in the U.S.
ContributorsMiralha, Lorrayne (Author) / Muenich, Rebecca L. (Thesis advisor) / Garcia, Margaret (Committee member) / Xu, Tianfang (Committee member) / Myint, Soe W. (Committee member) / Arizona State University (Publisher)
Created2021
Description
The world has been continuously urbanized and is currently accommodating more than half of the human population. Despite that cities cover only less than 3% of the Earth’s land surface area, they emerged as hotspots of anthropogenic activities. The drastic land use changes, complex three-dimensional urban terrain, and anthropogenic heat emissions alter the transport of mass, heat, and momentum, especially within the urban canopy layer. As a result, cities are confronting numerous environmental challenges such as exacerbated heat stress, frequent air pollution episodes, degraded water quality, increased energy consumption and water use, etc. Green infrastructure, in particular, the use of trees, has been proved as an effective means to improve urban environmental quality in existing research. However, quantitative evaluations of the efficacy of urban trees in regulating air quality and thermal environment are impeded by the limited temporal and spatial scales in field measurements and the deficiency in numerical models.
This dissertation aims to advance the simulation of realistic functions of urban trees in both microscale and mesoscale numerical models, and to systematically evaluate the cooling capacity of urban trees under thermal extremes. A coupled large-eddy simulation–Lagrangian stochastic modeling framework is developed for the complex urban environment and is used to evaluate the impact of urban trees on traffic-emitted pollutants. Results show that the model is robust for capturing the dispersion of urban air pollutants and how strategically implemented urban trees can reduce vehicle-emitted pollution. To evaluate the impact of urban trees on the thermal environment, the radiative shading effect of trees are incorporated into the integrated Weather Research and Forecasting model. The mesoscale model is used to simulate shade trees over the contiguous United States, suggesting how the efficacy of urban trees depends on geographical and climatic conditions. The cooling capacity of urban trees and its response to thermal extremes are then quantified for major metropolitans in the United States based on remotely sensed data. It is found the nonlinear temperature dependence of the cooling capacity remarkably resembles the thermodynamic liquid-water–vapor equilibrium. The findings in this dissertation are informative to evaluating and implementing urban trees, and green infrastructure in large, as an important urban planning strategy to cope with emergent global environmental changes.
This dissertation aims to advance the simulation of realistic functions of urban trees in both microscale and mesoscale numerical models, and to systematically evaluate the cooling capacity of urban trees under thermal extremes. A coupled large-eddy simulation–Lagrangian stochastic modeling framework is developed for the complex urban environment and is used to evaluate the impact of urban trees on traffic-emitted pollutants. Results show that the model is robust for capturing the dispersion of urban air pollutants and how strategically implemented urban trees can reduce vehicle-emitted pollution. To evaluate the impact of urban trees on the thermal environment, the radiative shading effect of trees are incorporated into the integrated Weather Research and Forecasting model. The mesoscale model is used to simulate shade trees over the contiguous United States, suggesting how the efficacy of urban trees depends on geographical and climatic conditions. The cooling capacity of urban trees and its response to thermal extremes are then quantified for major metropolitans in the United States based on remotely sensed data. It is found the nonlinear temperature dependence of the cooling capacity remarkably resembles the thermodynamic liquid-water–vapor equilibrium. The findings in this dissertation are informative to evaluating and implementing urban trees, and green infrastructure in large, as an important urban planning strategy to cope with emergent global environmental changes.
ContributorsWang, Chenghao (Author) / Wang, Zhihua (Thesis advisor) / Myint, Soe W. (Committee member) / Huang, Huei-Ping (Committee member) / Mascaro, Giuseppe (Committee member) / Arizona State University (Publisher)
Created2019