An efficient, cost-effective, and environmentally friendly protocol for extracting microplastics from soil samples

As land plastic pollution has accumulated over recent decades, small fragments of its degradation, microplastics (MPs) [1], have become an increasingly urgent problem in soil environments. Monitoring and reporting soil MPs will be essential in the future, but existing literature describes many protocols, none of which appear to be efficient for this purpose. The initial step in MP analysis from soils is extracting MP particles, which is particularly challenging due to the substrate [2]. Challenges include aggregate formation and the presence of other organic particles of similar size, complicating the development of efficient and reliable extraction protocols. Density separation methods are commonly used, and finding solutions that are effective, affordable, and environmentally friendly is crucial, with data comparability being vital for advancing knowledge on this topic. Here, we introduce an environmentally friendly protocol based on density separation using a sucrose solution. Its effectiveness for extracting MPs from soil was tested and validated. Validation results showed that this method efficiently recovered polyethylene (PE) for all tested MP sizes (>32 μm) and PVC for particles >500 μm, with high recovery rates. Extraction of 125–500 μm PVC is justified, despite a lower recovery rate of 64.04 ± 1.73%, because sucrose solution is practically free and environmentally safe, unlike previously used more expensive and toxic media. Validation results suggest that the proposed protocol has strong potential for extracting MPs from challenging soil samples. This method can be effectively used in any soil science laboratory, including those responsible for monitoring.