A Validated Method to Quantify Microplastic Contamination in Subsurface Seawater: A case study sampling the Sydney nearshore under sail

AIMS, in collaboration with The Clean Ocean Foundation, has completed this proof-of-concept study to facilitate further sampling of microplastics in the Southern Ocean (a joint collaborative initiative involving the Australian Institute of Marine Science (AIMS), the Integrated Marine Observing System (IMOS) and solo yachtswoman Lisa Blair). In this project, AIMS trialled density flotation and chemical digestion separation methods to process subsurface seawater samples and retrieve environmental microplastics. This report presents findings from controlled spike recovery tests as well as opportunistic field sampling events of subsurface waters processed with both separation methods. Opportunistic samples were collected along the NSW coastline in December 2021. Given the location of the sampling transects, this report also provides the first spatial baseline information on microplastic contamination in NSW waters adjacent to estuary outflows and urban outfalls. After trialling both separation methods, microplastics retrieved from the NSW samples were physically and chemically characterized used stereomicroscopy and spectroscopy, respectively. No statistical analysis were performed due to the low number of replicates. Results showed repeated chemical digestion employing potassium hydroxide solutions was most effective at microplastic recovery. Microplastics were retrieved from each of the eight samples collected in NSW subsurface seawaters, with polyethylene and polyester fibres being the most prevalent polymer types detected. The highest numbers of microplastics were recorded adjcent to the estuary outflows and urban outfalls present within the sampling area. Overall, the sampling and processing protocols developed here are allowing for the extension of the spatial coverage of microplastic data in seawaters.

澳大利亚海洋科学研究所（Australian Institute of Marine Science, AIMS）与清洁海洋基金会（The Clean Ocean Foundation）合作完成了此项概念验证研究，旨在推动南大洋（Southern Ocean）微塑料的进一步采样工作——该联合合作项目由澳大利亚海洋科学研究所（Australian Institute of Marine Science, AIMS）、综合海洋观测系统（Integrated Marine Observing System, IMOS）以及单人帆船选手丽莎·布莱尔（Lisa Blair）共同参与。本项目中，AIMS尝试了密度浮选法（density flotation）与化学消解分离法（chemical digestion separation methods），用于处理次表层海水（subsurface seawater）样本并提取环境微塑料。本报告呈现了两种分离方法对应的受控加标回收试验结果，以及采用两种分离方法处理的次表层海水机会性野外采样成果。机会性样本于2021年12月沿新南威尔士州（New South Wales, NSW）海岸线采集。鉴于采样断面的布设位置，本报告同时提供了新南威尔士州河口排污口与城市排污口邻近海域微塑料污染的首批空间基线数据。在对两种分离方法进行试验后，研究人员通过体视显微镜（stereomicroscopy）与光谱法（spectroscopy）分别对从新南威尔士州样本中提取的微塑料开展了物理与化学表征。因平行样数量较少，未开展统计学分析。结果显示，采用氢氧化钾溶液（potassium hydroxide solutions）进行反复化学消解的方法，在微塑料提取方面效果最佳。从新南威尔士州次表层海水采集的8个样本中均检出了微塑料，其中聚乙烯（polyethylene）与聚酯（polyester）纤维为检出占比最高的聚合物类型。采样区域内邻近河口排污口与城市排污口的海域，微塑料数量检出值最高。总体而言，本研究建立的采样与处理方案，为扩大海水微塑料数据的空间覆盖范围提供了可行路径。