Department of Crop & Soil Sciences, Washington State University, Pullman, WA, United States of America.
Department of Crop & Soil Sciences, Washington State University, Puyallup, WA, United States of America.
PLoS One. 2018 Nov 29;13(11):e0208009. doi: 10.1371/journal.pone.0208009. eCollection 2018.
Extraction and quantification of nano- and microplastics from sediments and soils is challenging. Although no standard method has been established so far, flotation is commonly used to separate plastic from mineral material. The objective of this study was to test the efficiency of flotation for the extraction of nano- and microplastics from biosolids and soil. We spiked biosolids and soil samples with polystyrene nano- and microbeads (0.05, 1.0, 2.6, 4.8, and 100 μm diameter). Different extraction methods (w/ and w/o H2O2 digestion) were tested, and plastic beads were separated from mineral particles by flotation in a ZnCl2 solution. Plastic particles were quantified by UV-Vis spectrometry and gravimetrically. While large beads (100 μm) could be quantitatively extracted (∼100%) from both biosolids and soils, smaller beads had low extraction efficiencies (ranging from 5 to 80%, with an average of 20%). Except for the 100 μm beads, oxidation with H2O2 negatively impacted the extraction efficiencies. For the soil, extraction with water only, followed by flotation in a ZnCl2 solution, resulted in relatively high extraction efficiencies (>75%) for beads larger than 1 μm, but low efficiencies (<30%) for the 0.05 and 1.0 μm beads. Our results indicate that while flotation generally works to separate plastic nano- and microbeads in a solution, the challenge is to quantitatively extract nano- and microbeads from a biosolids or soil matrix. Samples high in organic matter content require removal of the organic matter, but the common method of H2O2 oxidation leads to poor extraction efficiencies for nano- and microbeads.
从沉积物和土壤中提取和量化纳米和微塑料具有挑战性。尽管迄今为止尚未建立标准方法，但浮选通常用于将塑料与矿物材料分离。本研究的目的是测试浮选从生物固体和土壤中提取纳米和微塑料的效率。我们向生物固体和土壤样品中添加了聚苯乙烯纳米和微珠（0.05、1.0、2.6、4.8 和 100 μm 直径）。测试了不同的提取方法（有和无 H2O2 消化），并通过在 ZnCl2 溶液中浮选将塑料珠与矿物颗粒分离。通过紫外可见光谱法和重量法定量测定塑料颗粒。虽然可以从生物固体和土壤中定量提取（∼100%）较大的珠子（100 μm），但较小的珠子提取效率较低（范围为 5%至 80%，平均为 20%）。除了 100 μm 的珠子外，H2O2 的氧化作用会降低提取效率。对于土壤，仅用水提取，然后在 ZnCl2 溶液中浮选，对于大于 1 μm 的珠子，提取效率相对较高（>75%），但对于 0.05 和 1.0 μm 的珠子，提取效率较低（<30%）。我们的结果表明，虽然浮选通常可用于分离溶液中的塑料纳米和微珠，但挑战在于从生物固体或土壤基质中定量提取纳米和微珠。高有机质含量的样品需要去除有机质，但常用的 H2O2 氧化方法会导致纳米和微珠的提取效率降低。
