Degradation of biodegradable plastic films in soil: microplastics formation and soil microbial community dynamics

Biodegradable plastic poly(butylene adipate-co-terephthalate) (PBAT) has raised concerns regarding the release of PBAT microplastics and their potential environmental risks. In this study, PBAT plastic films were incubated in soil for 180 days to investigate the temporal evolution of PBAT microplastics and the dynamic responses of soil bacteria and fungi. The results showed that PBAT microplastics initially increased to a peak before decreasing by 74.7 % within 180 days. The predominant microplastics were film-shaped and smaller than 10 μm. Based on the temporal patterns, three distinct phases were identified: the initial release phase (0-30 days), the critical release phase (60-120 days), and the critical degradation phase (150-180 days). Notably, dominant fungal biomarkers with prevalent saprotrophic functions, particularly Humicola and Schizothecium, promoted the formation of PBAT microplastics by structurally fragmenting the PBAT film. In contrast, dominant bacterial biomarkers associated with dominant metabolic functions, such as Verrucomicrobiota, primarily contributed to the degradation of the PBAT microplastics by utilizing them as carbon sources. Our findings offer new insights into systematically evaluating the environmental behavior and potential environmental risks of biodegradable microplastics and provide a theoretical basis for strategies aimed at accelerating the degradation of biodegradable microplastics in soil environments.