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.

对环境中塑料废弃物开展监测，对于明晰该污染物的存量、来源、迁移路径、归趋以及环境影响至关重要。然而，目前针对湖床塑料废弃物的监测研究相对匮乏——而湖床是明晰淡水流域内塑料废弃物归趋与迁移路径的关键潜在研究环境。本研究中，研究人员采用自给式水下呼吸器（self-contained underwater breathing apparatus, SCUBA），在美国塔霍湖的5个采样点位沿样带开展湖床废弃物采集工作。采集所得的废弃物被带至地表，并按废弃物类别完成分类与表征。研究人员对塑料废弃物进行子采样，采用衰减全反射-傅里叶变换红外光谱（Attenuated Total Reflectance-Fourier Transform InfraRed, ATR-FTIR）法完成聚合物组分测定。5个潜水采样点位的湖床塑料废弃物平均采集密度为每千米83±49件。占比最高的塑料废弃物类别为“其他塑料废弃物”（即未归入其他类别的塑料废弃物），其次为食品容器、塑料袋、玩具以及容积小于2 L的瓶罐。上述结果与此前针对水下废弃物开展的研究结论一致，证实了塑料废弃物干预措施与持续性科普教育的必要性。子样本中检出频率最高的六种聚合物依次为聚氯乙烯、聚苯乙烯/发泡聚苯乙烯、聚对苯二甲酸乙二醇酯/聚酯、聚乙烯、聚丙烯以及聚酰胺。上述观测结果总体上契合全球塑料生产趋势，以及现有全球范围内湖泊表层水与沉积物中微塑料研究的汇总数据。研究发现部分废弃物子类别主要由单一聚合物类型构成，因此在那些无法测定聚合物组分但已完成废弃物分类的研究中，本研究结果可为特定子类别塑料废弃物的总聚合物组分提供估算依据。