SPATIAL DISTRIBUTION OF MICROPLASTIC POLYMERS IN THE WATER COLUMN OF A FRESHWATER DRINKING SUPPLY

Microplastics are an emerging issue in drinking water sources, but there are few studies focused on their distribution within the water column in freshwater systems. The purpose of this study was to investigate the distribution of various polymers throughout the water column and sediment. Our study site is a small reservoir of roughly 92 million gallon storage capacity prior to mechanical and chemical filtration for drinking. We sampled from six different locations within the reservoir based on bathymetry and influent and effluent circulation. At each location, samples were taken at the surface and then in 10m intervals to the sediment. Collections were processed using a density separation in sodium chloride, hydrogen peroxide digestion, and vacuum filtration through cellulose filters. Filters were weighed to determine estimated microplastic concentrations for each location and depth in the water column. We characterized microplastics by color, and fiber or fragment type for each sample. Identification of individual microplastics was determined using an attenuated total reflectance technique of Fourrier Transform Infrared (ATR-FTIR) spectroscopy compared to a known polymer library. Initial analysis indicates a clear separation in distribution of fibers versus fragments and that concentrations by depth are not uniform. Continuing analysis is directed toward characterizing the distribution by polymer type. Our results aim to illuminate the role polymer type play in determining the distribution and settling of microplastics in a reservoir prior to withdrawal for mechanical and chemical filtration. Such understanding may help to improve water circulation designs prior to filtration to improve drinking water quality.