Reliable, easy, cost-effective and reproducible ways of extracting microplastics (MP) from environmental samples remain important requirements for MP research. In this context, electrostatic separation is a new proposition, especially for extracting MP from mineral-rich samples and large sample volumes. However, there is little research evaluating the reliability of the technique. This study has evaluated the effectiveness of the Korona-Walzen-Scheider (KWS) system; a small-scale version of larger machines designed to sort recycling materials. Recovery rates of a variety of sizes of MP, spiked in beach sediments, were found to be highly dependent on the MP size. MP ≥ 2 mm achieved 99 – 100% recovery (with the exception of fibers: ∼80%), MP of 63–450 μm achieved ∼60–95% recovery and MP of 20 μm achieved ∼45% recovery. For particle-based analysis, additional density separation is still inevitable for the analysis of small MP after KWS separation and further reduces the overall recovery rates. Mass reduction rates of beach and commercial reference sand greatly differed, 93 and 17%, respectively. Mineral analysis using SEM-EDX suggested that lower reduction rates found in commercial sand was due to high presence of small (<50 μm) calcite particles. Tests based on environmental soil samples revealed comparatively low mass reduction rates (∼1%), suggesting that KWS treatment was inefficient for soils due to high levels of fine particulates. Sieving to remove fine particles improved mass reduction, though only to ∼15%. To specifically test for influence of fine particulates, recovery rates were determined for sand samples spiked with a defined amount of silicate dust, resulting in a reduction of certain MP recovery rates, especially medium-sized (450 μm) MP. Conclusively, several key influential parameters were identified, such as mineral composition and grain size, that can negatively effect sediment mass reduction as well as MP recovery rates. Given the variability in recovery rates, the use of internal standards is recommended when using the KWS, particularly for smaller MP (<500 μm). For large-volume (beach) sand samples, where interest is mainly in MP > 450 μm, electrostatic separation is a reliable and fast approach for MP extraction from the environment.

中文翻译：

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从富含矿物质的环境样品中静电分离微塑料的评价

从环境样品中提取微塑料 (MP) 的可靠、简便、经济高效和可重复的方法仍然是 MP 研究的重要要求。在这种情况下，静电分离是一个新的命题，特别是从富含矿物质的样品和大样品量中提取 MP。然而，很少有研究评估该技术的可靠性。本研究评估了 Korona-Walzen-Scheider (KWS) 系统的有效性；一种用于对回收材料进行分类的大型机器的小规模版本。发现在海滩沉积物中掺入的各种大小的 MP 的回收率高度依赖于 MP 的大小。MP ≥ 2 mm 实现了 99 – 100% 的回收率（纤维除外：~80%），63–450 μm 的 MP 实现了 ~60–95% 的回收率，20 μm 的 MP 实现了 ~45% 的回收率。对于基于粒子的分析，对于 KWS 分离后的小 MP 的分析，额外的密度分离仍然是不可避免的，并进一步降低了整体回收率。海滩和商业参考沙的质量减少率差异很大，分别为 93% 和 17%。使用 SEM-EDX 的矿物分析表明，在商业砂中发现较低的还原率是由于小（<50 μm）方解石颗粒的大量存在。基于环境土壤样​​品的测试显示质量减少率相对较低（~1%），表明 KWS 处理对土壤效率低下，因为细颗粒物含量高。筛分去除细颗粒改善了质量减少，但仅减少了约 15%。为了专门测试细颗粒物的影响，确定了掺入一定量硅酸盐粉尘的砂样品的回收率，导致某些 MP 回收率降低，尤其是中型 (450 μm) MP。最后，确定了几个关键的影响参数，例如矿物成分和粒度，它们会对沉积物质量减少和 MP 回收率产生负面影响。鉴于回收率的可变性，建议在使用 KWS 时使用内标，特别是对于较小的 MP (<500 μm)。对于大体积（海滩）沙子样品，其中感兴趣的主要是 MP > 450 μm，静电分离是从环境中提取 MP 的可靠且快速的方法。这会对沉积物质量减少和 MP 回收率产生负面影响。鉴于回收率的可变性，建议在使用 KWS 时使用内标，特别是对于较小的 MP (<500 μm)。对于大体积（海滩）沙子样品，其中感兴趣的主要是 MP > 450 μm，静电分离是从环境中提取 MP 的可靠且快速的方法。这会对沉积物质量减少和 MP 回收率产生负面影响。鉴于回收率的可变性，建议在使用 KWS 时使用内标，特别是对于较小的 MP (<500 μm)。对于大体积（海滩）沙子样品，其中感兴趣的主要是 MP > 450 μm，静电分离是从环境中提取 MP 的可靠且快速的方法。