Weathering of plastics in terrestrial environments

When accumulating in the terrestrial environment plastics undergo weathering, altering their properties and fragmenting into micro- and submicron plastics. Although various analytical methods exist to study these processes, a comprehensive overview of their application and the alterations of plastics under field conditions across different terrestrial systems is missing. This review summarises analytical approaches for assessing surface, structural, chemical and mechanical changes in weathered plastics, focusing on scanning electron microscopy. We examine plastic alterations in short-term (e.g., composting, wastewater treatment) and long-term (e.g., landfills, soils) systems. As sample treatment substantially alters analyses, we provide recommendations for assessing these changes. Plastic weathering leads to significant, but comparable, changes across terrestrial systems, with plastic properties as key influencing factors. While most data come from landfill studies, research in soils remains limited. Understanding long-term weathering is essential for evaluating the environmental fate of plastics, emphasizing the need for extended studies in diverse terrestrial environments. • SEM surface change comparisons are hampered by different technical settings • Terrestrial weathering causes similar alterations in plastic properties across all systems • Plastic colour and thickness influence weathering behaviour • Long-term weathering data available for landfills but scarce for soils • Weathering will substantially affect the further fate of plastics