Generation of biodegradable microplastics from commercially available PBAT and PLA-based plastic bags in water: Impacts of UVA and water medium

This study investigated the abiotic degradation potential of two commercially available biodegradable plastic bags, primarily composed of poly(butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA), in ultrapure water (UW) and artificial seawater (ASW) under UVA light and dark conditions at 30 ± 1 °C over a 12-week period. Degradation behavior was evaluated based on weight loss, morphological changes, carbonyl index (CI), dissolved organic carbon (DOC) generation, microplastic formation, and water analysis. Results indicated that both PBAT and PLA degraded more rapidly in UW than in ASW, with UVA light markedly enhancing the degradation rate. Surface analysis revealed that PBAT degradation primarily occurred through bulk erosion, whereas PLA degradation involved both bulk and surface erosion. PBAT experienced substantial weight loss, while PLA showed a more rapid increase in CI, suggesting greater susceptibility to hydrolysis. Water analysis revealed pH fluctuations, DOC release, and the presence of microplastics (MPs), indicating ongoing hydrolytic and oxidative degradation. The presence of MPs was further confirmed by Nile Red (NR) tagging and ImageJ analysis, which identified a variety of particle shapes, primarily fragments and fibers. MP size and distribution analysis using ImageJ demonstrated that both plastic types contributed significantly to MP formation. Overall, these findings suggest that commercially available biodegradable plastic bags undergo incomplete degradation in aquatic environments and may persist in seawater in a manner similar to conventional plastics. These results highlight the need for further research to enhance the design and environmental performance of biodegradable plastics, particularly with regard to their degradation behavior in marine conditions.