Microplastics in Terrestrial Ecosystems: Detection, Transport Pathways, and Ecotoxicological Risks

Microplastics are becoming well-known as chronic pollutants of terrestrial ecosystems, although their sources, dynamics of transportation, reliability of detection and ecological hazard are not evenly described. This review is a synthesis of the existing information about microplastics in soils, including analytical detection and characterization techniques, the major sources in the terrestrial environment, transport routes within the compartments and between compartments, and reported ecotoxicological consequences on soil biota, plants, and microbial communities. We also critically discuss the strengths and weaknesses of methodologies, making the distinction of sampling design differences, size detection limits, polymer identification methods, and quality assurance procedures on data comparability and uncertainty. An important outcome of this review is the systematic evaluation of the strength of evidence in three interrelated areas: measurement, environmental transport, and biological impacts, hence explaining which findings are strong and in which areas of research significant knowledge gaps still exist. We also suggest a conceptual framework that strongly connects the measurement uncertainty to the exposure estimation, interpretation of risk, and management relevance. This review uses mechanistic insights into transport and ecotoxicology alongside analysis constraints to add to the more comprehensive foundation of terrestrial risk assessment. Lastly, we determine research priorities, such as harmonized methodologies, realistic exposure scenarios, and cross-scale monitoring strategies, in order to assist in the science-based policies and mitigation action.