Soil microplastic analysis: a harmonized methodology

Microplastics (MPs) are contaminants of global concern, especially considering their widespread use. However, a systematic and comprehensive analytical procedure is not yet standardized for MPs in soils. Most of the methods have primarily been modified from existing marine research without acknowledging the inherent complexities of sampling and analyzing MPs in soil ecosystems. This review critically evaluates existing sampling, separation, identification, and quantification methods for MPs in soils and proposes a comprehensive methodology comprising eight phases for analyzing MPs in soils. We emphasize the importance of the soil sampling planning phase before conducting soil MP analyses and the necessity to assess physicochemical properties. Novel methods should be developed, and existing analytical approaches must be adequately modified and refined, given the heterogeneity of soils. Soil MP analyses should be coordinated globally by utilizing existing networks and infrastructure for soils, crops, and food security research and biomonitoring in conjunction with environmental and material sciences. This critical review may be an effective model for developing global standards for MP analysis in soils, focusing on the new regulations initiated by the UNEP to develop a legally binding agreement on plastic pollution.