An optimized density-based approach for extracting microplastics from soil and sediment samples

Microplastic pollution in the environment has received growing attention worldwide. A major impediment for accurate measurements of microplastics in environmental matrixes is to extract the particles. The most commonly-used method for separation from soil or sediment is flotation in dense liquid based on the relatively low density of plastic particles. This study provides an improved and optimized process for extraction of microplastic particles by modifying the floatation technique and floatation solution. Microplastics in soils and sediments are extracted by adding 200 g dry soil or sediment sample to 1.3 L mix of the saturated NaCl and NaI solutions in a volume ratio of 1:1 and aerating for 40 s then filtering the supernatant. The accuracy and precision of the new approach is validated by recovery experiments using soil and sediment samples spiked with six common microplastic compounds: polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and expanded polystyrene (EPS), and comparison with the previous method. The optimized approach is further compared with the previous approach using the real soil and sediment samples.