Dissertation
EXPLORATION OF MICROPLASTIC FIBERS TRANSPORT DYNAMICS IN POROUS MEDIA USING A COMBINATION OF PHYSICAL EXPERIMENTS AND NUMERICAL SIMULATIONS
Washington State University
Doctor of Philosophy (PhD), Washington State University
05/2024
DOI:
https://doi.org/10.7273/000006594
Abstract
The existence of microplastics (MPs) in the environment has been a growing concern for two and a half decades, having now been found in remote areas, ocean sediment, deserts, and mountain peaks. MPs in the environment are a concern because they can impact soil properties and organisms. Research has determined that MPs can affect aquatic organisms in two forms: 1.) mechanical- MPs can attach to the body of the organism and impact their movement and 2.) chemical- the leaching of chemicals from the MPs can be absorbed by the organisms, both of these impact forms can lead organisms to experience inflammation, stress, death, and reproduction decline. The impact on human health is limited but assumed to see the same impacts as aquatic organisms. The largest MP type by mass found in the environment is microplastic fiber (MPF). Scientists understand where MPs come from and where they end up (large-scale movement), the missing aspect is how they move. This research gap is missing due to the transport mechanics occur at the pore scale which is difficult to capture. The mechanisms of MPFs transport have been proposed numerically but have not been validated. This research collected MPF transport data in a 2D laboratory model to understand the transport dynamics in porous media of three different lengths 0.3, 0.5, 0.8 cm and microbeads to act as a passive tracer, modeling MPF transport with existing simulation tools (ADE equation) and validate the only MPF distributed simulation model to date. Videos captured the trajectory of the fiber and beads, and the trajectory data was used to generate breakthrough curves. The experimental data found that fibers tumble/roll during their transport through the model, that fibers traveled much slower than expected, and longer fibers would travel slower. It was observed that fibers would have an abrupt change in velocity and became stuck then re-mobilized. This paper refers to this dynamic as “trapping”. Comparisons to
the ADE (i.e. advection-dispersion models) equation and the distributed simulation model (DSM) were unable to simulate MPF transport, which leads to the question of what dynamics are missing from the models. ADE simulation was unable to capture the correct shape of the curve, with particles arriving sooner than the experiments. The DSM can simulate the transport of beads but nothing else. This suggests that the missing dynamics result in a retention or trapping process, but the design of these experiments cannot determine the precise mechanism. However, two upscaled representations of the trapping process were able to significantly improve the agreement of the experimental and numerical results.
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Details
- Title
- EXPLORATION OF MICROPLASTIC FIBERS TRANSPORT DYNAMICS IN POROUS MEDIA USING A COMBINATION OF PHYSICAL EXPERIMENTS AND NUMERICAL SIMULATIONS
- Creators
- Tyler T. Fouty
- Contributors
- Nick Engdahl (Chair)Lazaro Perez (Committee Member)Courtney Gardner (Committee Member)Jan Boll (Committee Member)Alex Fremier (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 82
- Identifiers
- 99901122441101842
- Language
- English
- Resource Type
- Dissertation