Environment changes everything. How relevant are laboratory studies of sorption of pollutants on microplastics? A critical review

The rapid increase in global plastic production, reaching hundreds of millions of metric tons annually, has led to significant environmental challenges, primarily due to the widespread mismanagement of plastic waste. In the environment, plastic waste undergoes degradation, leading to the formation of microplastics (MPs), which can act as vectors for various inorganic and organic pollutants that are adsorbed on them. This review critically evaluates the relevance of laboratory-based studies on pollutant sorption by MPs in comparison to real-world environmental scenarios. Laboratory experiments often simplify natural environments by employing pristine MPs under controlled conditions, which limits the applicability of findings to complex aquatic ecosystems. Key factors, such as biofilm formation, abiotic weathering, and the presence of plastic additives, significantly influence the sorption behaviour of MPs. For example, biofilms enhance the adsorption of metals and organic pollutants, while abiotic weathering alters surface properties, reducing hydrophobicity and facilitating the sorption of hydrophilic contaminants. The review underscores the need to integrate these factors into future studies to improve understanding of MPs' roles in pollutant dynamics within real aquatic environments. Additionally, it identifies critical gaps in knowledge, particularly concerning the long-term interactions between MPs and pollutants in natural settings, and emphasizes the importance of comprehensive research that simulates environmental conditions.