Publication Date

2025

Document Type

Dissertation/Thesis

First Advisor

Lenczewski, Melissa E.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Geology and Environmental Geosciences

Abstract

Microplastics (MPs) are synthetic polymer particles less than 5 mm in size that originate from both primary manufacturing and the breakdown of larger plastics. Extensive studies have examined their occurrence in other environments, while little is known about their presence and behavior in groundwater, especially in urbanizing regions in Southeast Asia. This study investigates the occurrence and abundance of microplastics within groundwater systems of Nakhon Pathom, an urbanizing province in central Thailand.

Groundwater was collected representing shallow and deep aquifers between May 2023 and May 2025. The analyses included physical-chemical parameters, major ions, heavy metals, and microplastic abundance and composition. Microplastics were identified and characterized using Laser Direct Infrared (LDIR) imaging, and statistical relationships between microplastic abundance and groundwater quality were explored.

The results show groundwater quality is stable with the shallow aquifer has higher salinity which impacted from late quaternary marine transgression caused the shallow aquifer to predominantly exhibit a Na–Cl water type from saltwater trapped while the deep aquifer displays a mixed water type remained stable throughout the study. This indicated that the urbanizing phase in the province has not yet progressed to the point of significantly altering groundwater. Microplastics were detected with concentrations ranging from 484 to 2,007 particles/L, dominated by particles 20–50 µm in size with the highest abundance was found in the shallow aquifer. The most common polymers were polypropylene (PP), polytetrafluoroethylene (PTFE), and polyamide (PA), which are commonly used on a daily basis as packaging, non-stick items, and synthetic fibers for clothing. There was no significant correlation found between microplastic abundance and major ions and salinity, indicating that microplastic occurrence is primarily controlled by physical transport mechanisms rather than chemical interactions. Seasonal variation between wet and dry periods was minimal, likely linked to the El Niño event that affected Thailand during the study period. Rubber particles, also detected in both aquifers, were derived from tire wear particles transported via runoff and infiltration pathways.

This study partially supports the hypothesis that microplastic abundance varies by aquifer depth, with higher contamination in shallow aquifers. However, the absence of correlation between microplastics and chemical parameters emphasizes the dominance of physical processes in microplastic transport.

Extent

115 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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