Date of Award

8-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Hydrogeology

Committee Chair/Advisor

Dr. Kelly Best Lazar

Committee Member

Dr. Stefanie Whitmire

Committee Member

Dr. Elizabeth Carraway

Committee Member

Dr. David Ladner

Abstract

The role of microplastics as an emerging contaminant can be complex to study because of the lack of standardization in the collection and analysis of microplastic particles. The purpose of this manuscript is to detail an iterative process of different collection methods in trying to understand microplastic deposition and transport in a freshwater micro-watershed through lab-based and field-based studies. A flume experiment was conducted to test the trapping efficiency of a sediment trap design at two different velocities (1.12 m/s and 2.24 m/s). Eight types of microplastics varying in morphology and density were introduced to the flume in order to test the sediment trap’s trapping efficiency of different microplastic particles. The results demonstrated that the sediment trap did not trap microplastics preferentially based on velocity, which was promising for deployment in a natural environment. To test the effect of stream restoration on sediment and microplastic deposition within Lower Hunnicutt Creek (LHC), a depositional study was devised using the sediment trap design from the flume experiment. After successful deployment at two separate study sites along LHC, several unsuccessful attempts at sediment trap recovery followed due to raised water levels and high turbidity. The research design shifted from a sediment depositional study to a microplastic transport study in the surface water of Hunnicutt Creek with 80-µm plankton nets. Five study sites throughout the Hunnicutt Creek watershed were used to collect 10 m3 of surface water at each sampling site during each sampling event. The results of the surface water microplastic study indicate that the microplastic abundance increases down the watershed of Hunnicutt Creek. A series of paired t-tests demonstrated a significant difference in the microplastic abundance of adjacent sampling sites down the watershed. All three studies described here contribute to the knowledge of microplastic depositional and surface water sampling methods within freshwater micro-watersheds.

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