Degradation Pathways of Biodegradable Films in Aquatic Ecosystems: the Role of Environmental Factors in Microplastics Formation

In recent years, biodegradable plastics have increasingly emerged as promising alternatives to conventional plastics, which contribute significantly to environmental pollution due to their persistence in the environment. The global market for biodegradable plastics in packaging is continuously expanding, with a projected compound annual growth rate (CAGR) of 12.4% by 2030. As a result, growing attention has been directed toward evaluating their environmental impact and interactions with biological systems. Studies have shown that, under natural conditions, the rapid and complete degradation of biodegradable plastics is rare. In fact, these materials may fragment into microplastics more quickly than conventional plastics, thus posing a potential environmental hazard. The mechanisms of biodegradation—and consequently the formation of biodegradable microplastics (BMPs)—are strongly influenced by the polymer type and its intrinsic properties. Moreover, polymer degradation in natural environments results from a complex interplay between abiotic factors (such as UV radiation, temperature, pH, humidity, and hydrolysis) and biotic processes driven by microbial activity. Abiotic conditions initiate surface deterioration—via photodegradation and oxidative hydrolysis—weakening the polymer matrix and facilitating microbial colonization. Microorganisms then further fragment the material using extracellular enzymes, accelerating the generation of microplastics. Recent evidence also suggests that aquatic plants may play an active role in these degradation processes, either by modifying the local microenvironment—e.g., through oxygen release and surface interactions—or by directly interacting with and potentially absorbing microplastic particles released during polymer breakdown. These dynamics could significantly influence the environmental fate and ecological impact of biodegradable plastics in aquatic ecosystems. In light of these considerations, the aim of this work was to investigate the influence of UVC radiation on the degradation of biodegradable films based on PLA and its blends. Laboratory-scale experiments were carried out to assess the effect of UVC irradiation on microplastic formation from blown PLA-based films in different aquatic media, over an observation period of up to 12 weeks. Changes in pH were monitored, while the morphology, size, wettability, crystallinity, and mechanical properties of the generated microplastics were analyzed to evaluate the degradation behavior compared to the neat materials. The results showed that UVC-treated biopolymers degraded more rapidly than untreated ones, producing smaller particles while maintaining similar morphology. Among all tested films, PLA proved to be the most sensitive to photodegradation, whereas PBS exhibited the greatest stability. The PBS/PLA blend displayed intermediate behavior between the two pure biopolymers. DSC analysis revealed that both UV exposure and water conditioning affected the organization of the crystalline structure in the treated films.