Division of Environmental Engineering, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Ube, Yamaguchi, Japan.
Division of Environmental Engineering, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Ube, Yamaguchi, Japan.
Sci Total Environ. 2021 May 10;768:144655. doi: 10.1016/j.scitotenv.2020.144655. Epub 2021 Jan 6.
Rivers are vital for understanding freshwater microplastics pollution, along with the conduits from land-sources to marine-sinks. In this study, we investigated microplastics in the small-scale Awano and Ayaragi rivers, which flow into the Sea of Japan (SJ), and the Asa and Majime rivers, which flow into the Seto Inland Sea (SIS) in Yamaguchi Prefecture, Japan. Surface water samples were collected from 29 stations. Filtration, wet peroxidation, and density separation methods were employed to extract microplastics. Polymers were identified via attenuated total reflectance-Fourier transform infrared spectroscopy. Microplastics abundances and comparisons among different rivers revealed that these small-scale rivers were highly polluted than others around the world. Characterization demonstrated that small microplastics (<1000 μm) in size, fibers and fragments in shape and the polymers-polyethylene, polypropylene, vinylon, polyethylene terephthalate, and polystyrene were dominant. These small-scale rivers emitted substantially higher quantities of Japan land-sourced microplastics (0.4-154.27 billions/day and 0.01-17.55 tons/day) into the SJ and SIS environments than larger rivers in other countries compared to basin areas. The pollution load index indicated that all the river stations were polluted with microplastics. An assessment of the polymeric and pollution risks revealed variably low to high risks. The higher were the abundances of microplastics and toxic polymers, the higher were the pollution level and risks. The sites at high risk of pollution were regarded as hotspots. Both point and non-point land-uses sources of pollution could release microplastics into the river freshwater environments, affected posing high risks and hotspots. Moreover, the pollution characteristics (shapes-sizes-polymers) indicated serious ecotoxicological threats to these rivers and their downstream environments. This study provided new insights into river microplastics pollution and revealed small-scale rivers to be prominent source-to-sink microplastics conduits. Risk assessments provided a baseline for future comprehensive assessments and developing practical approaches to wards setting water quality criteria, pollution control and management.
河流对于了解淡水微塑料污染以及陆地源向海洋汇输送的途径至关重要。本研究调查了流入日本海的小安野川和绫罗川以及流入日本山口县濑户内海的朝川西川和舞元川中的微塑料。从 29 个站点采集了地表水样本。采用过滤、湿过氧化物和密度分离方法提取微塑料。通过衰减全反射傅里叶变换红外光谱法鉴定聚合物。微塑料丰度以及不同河流之间的比较表明，这些小河流的污染程度高于世界其他地区的河流。特征描述表明，主导的微塑料是尺寸小于 1000μm 的小颗粒、纤维和碎片形状以及聚合物——聚乙烯、聚丙烯、维尼纶、聚对苯二甲酸乙二醇酯和聚苯乙烯。与其他国家的大型河流相比，这些小河流向日本海和濑户内海环境排放的日本陆地源微塑料数量要高得多（每天 0.4-154.27 亿至 0.01-17.55 吨），与流域面积相比。污染负荷指数表明，所有河流站点都受到微塑料的污染。对聚合物和污染风险的评估表明，风险从低到高不等。微塑料和有毒聚合物的丰度越高，污染水平和风险就越高。被认为存在高污染风险的地点是热点。点源和非点源污染都可能将微塑料释放到河流水体环境中，从而构成高风险和热点。此外，污染特征（形状-大小-聚合物）表明，这些河流及其下游环境受到严重的生态毒性威胁。本研究为河流微塑料污染提供了新的见解，并表明小河流是重要的源汇微塑料输送途径。风险评估为未来的综合评估提供了基线，并为制定水质标准、污染控制和管理的实用方法提供了依据。
