Polymer characterization of submerged plastic litter from Lake Tahoe, United States

Monitoring plastic litter in the environment is critical to understanding the amount, sources, transport, fate, and environmental impact of this pollutant. However, few studies have monitored plastic litter on lakebeds which are potentially important environments for determining the fate and transport of plastic litter in freshwater basins. In this study, self-contained underwater breathing apparatus (SCUBA) was used for litter collection at the lakebed along transects at five locations in Lake Tahoe, United States. Litter was brought to the surface and characterized by litter type. Plastic litter was subsampled for polymer determination using Attenuated Total Reflectance-Fourier Transform InfraRed (ATR-FTIR) spectroscopy. The average plastic litter recovered from the lakebed for the five dive sites was 83 ±49 items per kilometer. The top plastic litter categories were other plastic litter (i.e. plastic litter that did not fall in another category), followed by food containers, plastic bags, toys, and bottles <2 L. These results are in line with prior studies on submerged litter, supporting that intervention approaches or ongoing education is needed. The six polymers most frequently detected in the subsamples were polyvinyl chloride, polystyrene/expanded polystyrene, polyethylene terephthalate/polyester, polyethylene, polypropylene, and polyamide. These observations generally reflect the global plastic production trend and global compilations of microplastic studies from lake surface water and sediments. We found that some litter subcategories were primarily comprised of a single polymer type, therefore, in studies where the polymer type cannot be measured but litter is categorized, these results could provide an estimate of the total polymer composition for select subcategories.