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Polymer Characterization of Submerged Plastic Litter from Lake Tahoe, United States
Summary
Researchers used SCUBA diving to survey plastic litter on the floor of Lake Tahoe and found an average of 83 plastic items per kilometer of lakebed. The most common polymers matched those found in surface-water microplastic studies globally — polyvinyl chloride, polystyrene, polyethylene terephthalate, polyethylene, polypropylene, and polyamide. The study reveals that lakebeds act as long-term sinks for plastic pollution, with the accumulating debris representing both an ongoing source of microplastics as it fragments and a persistent contamination of freshwater ecosystems.
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, a self-contained underwater breathing apparatus was used for litter collection at the lakebed along five transects in Lake Tahoe, United States. Litter was brought to the surface and characterized by litter type. Plastic litter was subsampled, and polymer composition was determined using attenuated total reflection Fourier transform infrared spectroscopy. The average plastic litter from the lakebed for the five dive transects was 83 ± 49 items per kilometer. The top plastic litter categories were other plastic litter (plastic litter that did not fall in another category), followed by food containers, bottles <2 L, plastic bags, and toys. These results are in line with prior studies on submerged litter, and intervention approaches or ongoing education are 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 reflect global plastic production and 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 litter categories.