Electronic Theses and Dissertations

Date

2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Civil Engineering

Committee Chair

Farhad Jazaei

Committee Member

Brian Waldron

Committee Member

Charles Camp

Committee Member

David Arellano

Committee Member

Kati Bell

Abstract

The global escalation of plastic production has led to widespread microplastic (MP) contamination across terrestrial and aquatic environments, posing a growing environmental challenge. MPs, defined as plastic particles smaller than 5 mm, originate from the degradation of larger plastics as well as from direct inputs such as synthetic fibers, biosolids, and agricultural mulching films. Despite their ubiquity, limited knowledge exists regarding their behavior in soils and their influence on soil–water–plant interactions. This dissertation addresses this gap through an integrated series of controlled laboratory experiments and modeling analyses that examine how MPs modify soil–water–plant dynamics, how they are transported through infiltration and runoff under simulated rainfall events, and how advanced analytical tools can be used for their precise detection, identification, and quantification. The results demonstrate that MPs fundamentally alter soil hydraulic properties by modifying pore connectivity, surface hydrophobicity, and water retention behavior. These changes affect soil moisture storage, infiltration, and evapotranspiration patterns, potentially influencing plant growth, root development, and irrigation efficiency. Beyond the root zone, altered infiltration and runoff dynamics accelerate surface erosion, promote lateral and vertical particle migration, and enhance the likelihood of MP transfer to groundwater and downstream water bodies. Over time, such pathways enable the progressive delivery of terrestrial MP to rivers, estuaries, and ultimately marine ecosystems, intensifying global plastic circulation and contamination. This research highlights that even trace MP concentrations—at environmentally relevant levels—can lead to cumulative hydrological, agronomic, and ecological consequences. By integrating hydrological modeling, soil–water retention analyses, and particle-scale characterization using micro-FTIR spectroscopy, this dissertation establishes a mechanistic framework for understanding MP–soil interactions under realistic environmental conditions. The findings provide critical insights for predicting the fate and transport of MPs within agricultural landscapes, advancing sustainable soil and water resource management, and supporting the development of mitigation strategies that address the terrestrial origins of plastic pollution.

Comments

Data is provided by the student.”

Library Comment

Dissertation or thesis originally submitted to ProQuest.

Notes

Open Access

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