Abstract：
The ubiquitousness of microplastics (<5 mm) has become a pressing environmental concern globally due to the extensive use of plastics. Microplastics have been well-studied in aquatic environments but not well-characterized in soils. Present analytical processes to quantify microplastics accurately in soil samples are quite challenging and require improved and validated analytical steps to eliminate the obscurities and biases. We aimed to develop an effective method for the extraction and quantification of microplastics from soil samples. Different ratios of low-(NaCl) and high-density solutions (ZnCl2/ NaBr) were tested to determine the most efficient combination for density-dependent separation of microplastics from soil. The combination of low- (1:6) and high-density (1:3) solutions {as weight of soil(g)/volume of density solution(ml)} accounted for 95% recovery of the spiked microplastic particles from soil samples. Likewise, different soil-to-solution ratios of H2O2 were tested for the removal of soil organic matter with heating and non-heating steps. Prior removal of organic matter from soil samples achieved a clear supernatant that facilitated 99% recovery of microplastic particles. The validation of individually spiked microplastic particles of small (10-100 μm) and large scale (100-5000 μm) resulted in recovery ranging from 88 to 99%. A validated modified method with prior digestion followed by density-dependent separation was further tested using the field samples with microplastic contamination. The microplastics of different shapes, sizes, colours and polymeric compositions were reported efficiently and well characterized in the field-collected soil samples using this method.
摘要：
由于塑料的广泛使用,微塑料(<5mm)的普遍存在已成为全球紧迫的环境问题。微塑料已经在水生环境中得到了充分的研究，但在土壤中没有得到很好的表征。目前用于精确量化土壤样品中微塑料的分析过程非常具有挑战性，需要改进和验证的分析步骤来消除模糊和偏见。我们旨在开发一种从土壤样品中提取和定量微塑料的有效方法。测试了不同比例的低（NaCl）和高密度溶液（ZnCl2/NaBr），以确定最有效的组合，以根据密度从土壤中分离微塑料。低（1：6）和高密度（1：3）溶液的组合{土壤重量（g）/密度溶液体积（ml）}占土壤样品中加标微塑料颗粒的95％回收率。同样，通过加热和非加热步骤，测试了不同的H2O2土壤与溶液比对土壤有机质的去除。事先从土壤样品中去除有机物可获得澄清的上清液，从而促进了99％的微塑料颗粒回收。对小尺寸（10-100μm）和大尺寸（100-5000μm）的单独加标微塑料颗粒的验证，回收率为88％至99％。使用具有微塑料污染的现场样品进一步测试了经过验证的改良方法，该方法先进行消化，然后进行密度依赖性分离。不同形状的微塑料，尺寸,使用此方法在现场收集的土壤样品中有效地报道了颜色和聚合物组成，并对其进行了很好的表征。
