Soil Microplastic Extraction Efficiency Depends on the Sample Incubation Time and the Organic Matter Removal Agent Used

Environmental pollution by microplastics is now a global problem, as global plastic production is increasing and at the same time recycling of plastic waste is low. In recent years, a number of methods have been developed to determine the content of microplastics in soil. This study compares the efficiency of microplastic extraction in two-week and three-month incubation samples from three different soils artificially contaminated with different types of microplastics. H₂O₂ and KOH were used as agents to remove organic matter. The effects of changing the incubation time were significant in soils with a high organic matter content. A longer incubation time resulted in a lower efficiency of microplastic extraction. Compared to the results obtained with the control method after a two-week incubation, the loose sand samples achieved a similar extraction efficiency (86%), the amount of MP recovered in the uncontaminated sandy clay samples was 75%, while the sandy clay soils contaminated with heavy metals was 44%. The samples without organic matter removal showed a significantly better recovery rate of microplastics than the samples treated with H₂O₂ and KOH.