Tracy D. Frank
Date of this Version
Hartstein, A.R. (2022) Microplastics in the sediment of the North Platte, South Platte, and Platte Rivers. M.S. thesis, University of Nebraska-Lincoln. UNL Digital Commons.
Microplastics are defined as small plastic particles that are less than five millimeters in size. While most microplastic research focuses on marine environments, the behavior of these particles in freshwater ecosystems, specifically in river sediments, is understudied. A large majority of studies of fluvial environments are located in urbanized areas. This study focuses on the Platte River system, one of the main waterways within the Mississippi-Missouri River Basin that flows mainly through grassland and cropland, providing insight into the level of microplastic pollution in areas of low population density. Results provide the first quantification of microplastic concentrations of river sediments in the central United States. Sixteen sampling locations span the length of the North Platte, South Platte, and Platte Rivers, starting in Colorado and Wyoming and ending near the confluence with the Missouri River. Samples were first sieved to isolate the sand size fraction. Microplastics were separated from sand by floatation in a ZnCl2 solution, extracted by vacuum filtering, and examined using a binocular microscope. Results show that microplastics are present in the sediment of every site. Urbanization and wastewater treatment plant locations play a role in the quantity of particles found. Samples located in and downstream of urbanized areas have greater amounts of particles than those from rural sites. Over 75% of the particles identified in the sediment are fibers, indicating synthetic fabrics are the dominant source of contamination. The prominence of fibers along the length of the river system may reflect the distribution of wastewater treatment plants located throughout the entirety of the Platte River system. The level of microplastic pollution in this rural setting is comparable to other global freshwater systems of similar population density and land use. Results confirm the role of the Platte River system as both a sink and potential source of microplastic debris to the Missouri River and beyond.
Advisors: Tracy D. Frank and Erin Haacker