Microplastics occurrence and distribution in two western arid river systems: the Truckee River and the Lower Colorado River
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Authors
Lukasik, Hannah Lee
Issue Date
2024
Type
Thesis
Language
en_US
Keywords
Arid , Freshwater , Microplastics , Plastics , Riverine , Rivers
Alternative Title
Abstract
Microplastics (MPs) have been classified as an emerging contaminant and are ubiquitous throughout the environment, especially in marine and freshwater aquatic systems. While many studies concerning MPs have been conducted in marine and freshwater lake environments, few have been conducted in arid riverine systems. Additionally, there has been a call from the MPs community to investigate the impact of seasonality and discharge rates upon MP contamination of freshwater systems. In this study, we sought to quantify and characterize MPs in the Truckee River, an internally draining freshwater river system, in the arid U.S. states of Nevada and California and the Lower Colorado River basin. The Lower Colorado River flows from the U.S. and forms the interstate border between California and Arizona and the international border between Mexico and the U.S. Due to the geographic location and flow direction of the Lower Colorado River, these flows have the potential to transport MP particles across international borders. Both rivers flow through a variety of land uses and portions of tribal land areas, are used for drinking water, and receive inflows of treated wastewater. Because the rivers are utilized for their drinking water, recreation, and serve as important aquatic habitats, assessing the MPs present in these systems is essential for determining risk to human and aquatic health. Plastic chemical identification was conducted using microscope enabled µ-Fourier Transform Infrared Spectroscopy (µFTIR). Results from these studies are compared to MP work in the surrounding land areas and MP studies conducted on freshwater river systems. MPs were found in both the Truckee River and the Lower Colorado River. Concentrations increased with anthropogenic impact downstream along the Truckee River, while MP concentrations showed less change in concentration moving downstream along the Lower Colorado River. Moreover, seasonal flow changes appeared to increase the concentrations of MPs found within the Truckee River samples. This work will inform potential sources of MPs to freshwater river environments, help to explain seasonal variability of MP concentrations in arid freshwater systems, and aid in the understanding of the international impact of MPs contributed by the Lower Colorado River to Mexico.