Faculty of Bioresources and Environmental Sciences, Ishikawa Prefectural University, 1-308 Suematsu, Nonoichi, Ishikawa, 921-8836, Japan.
Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, 24, O, Wake, Nomi, Ishikawa, 923-1224, Japan.
Chemosphere. 2022 Nov;307(Pt 1):135730. doi: 10.1016/j.chemosphere.2022.135730. Epub 2022 Jul 18.
The purpose of this study was to identify a method to accurately separate small microplastics (<100 μm) from soil and sediment. We initially conducted spike-and-recovery tests using polyethylene microbeads and density separation and found that the recovery rate of microplastic particles smaller than 100 μm was less than 60%. This result suggested that previous reports have underestimated the concentrations of microplastics smaller than 100 μm in soil. When polyvinyl pyrrolidone was added and dispersed in a heavy liquid, the recovery rate exceeded 90%, regardless of the microplastic particle size. This improved recovery rate was independent of the type of polymer (polyethylene, polypropylene, polystyrene, polyethylene terephthalate, or nylon 6) and the physicochemical properties of the soil (Andisols, Entisols, or Ultisols), and the method was also effective for marine and lake sediments. Using this method, we measured microplastic concentrations in paddy soil. The results showed that the most common particle size, 20-100 μm, accounted for 64% of all microplastics. Accurate separation from the soil of fractions smaller than 100 μm, which account for the majority of microplastics in soil, will enable an accurate assessment of the impact of microplastics on the soil ecosystem. The method identified in this study can serve as the basic technique for achieving that goal.
本研究旨在寻找一种准确分离土壤和沉积物中小微塑料（<100μm）的方法。我们最初使用聚乙烯微珠进行加标回收试验和密度分离，发现小于 100μm 的微塑料颗粒的回收率小于 60%。这一结果表明，之前的报告可能低估了土壤中小于 100μm 的微塑料浓度。当聚维酮（PVP）被添加并分散在重液中时，无论微塑料颗粒的大小，回收率均超过 90%。这种回收率的提高与聚合物的类型（聚乙烯、聚丙烯、聚苯乙烯、聚对苯二甲酸乙二醇酯或尼龙 6）和土壤的理化性质（壤土、旱成土或变性土）无关，该方法对于海洋和湖泊沉积物也同样有效。我们使用该方法测量了稻田土壤中的微塑料浓度。结果表明，最常见的粒径（20-100μm）占所有微塑料的 64%。准确分离土壤中占多数的小于 100μm 的微塑料部分，将有助于准确评估微塑料对土壤生态系统的影响。本研究中确定的方法可以作为实现这一目标的基本技术。
