Biodegradable plastic mulch films are increasingly used in agriculture as an environmentally friendly alternative to conventional plastics. They help retain soil moisture, suppress weeds, and improve crop productivity. However, their ability to break down safely in soil remains uncertain. A new study reveals that naturally occurring clay minerals, ultraviolet (UV) radiation, and soil burial depth play crucial roles in determining how these materials degrade.
Published in New Contaminants, the research investigated two commonly used biodegradable polymers, poly(butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA). The researchers examined how different clay minerals and soil environments affected their physical and chemical transformations.
"Biodegradable plastics are often considered a sustainable solution to agricultural plastic pollution, but their environmental behavior is far more complex than simply disappearing into the soil," said Wei Liu, the corresponding author of the study. "Our findings highlight how natural soil components can actively influence plastic degradation and why understanding these interactions is essential for evaluating environmental safety."
To investigate these processes, the researchers exposed PBAT and PLA films to controlled UV radiation in the presence of two common clay minerals, kaolinite and montmorillonite. They also examined degradation on the soil surface and at a burial depth of 10 centimeters over 60 days.
The results revealed three important findings.
First, PBAT degraded more readily than PLA under the experimental conditions. Its comprehensive aging index reached 24.02, nearly twice the value recorded for PLA (12.98). This indicates that the two biodegradable materials respond differently to environmental stress.
Second, kaolinite accelerated UV-induced plastic degradation more effectively than montmorillonite. Under UV exposure, PBAT films in the kaolinite treatment lost approximately 10.69% of their weight, compared with 4.84% under UV exposure without clay minerals. Kaolinite also promoted greater degradation of PLA.
Further analysis revealed why. Kaolinite absorbed light more effectively and facilitated electron transfer, generating higher levels of reactive oxygen species. These highly reactive molecules, particularly hydroxyl radicals, attacked polymer chains and accelerated their breakdown.
Third, plastic films buried 10 centimeters below the soil surface exhibited more pronounced degradation than films placed on the surface. Although UV radiation could barely penetrate this depth, soil moisture and mineral interactions promoted chemical reactions that contributed to polymer aging.
Advanced chemical analysis revealed that degradation involved the breaking of ester bonds and oxidation reactions, producing smaller molecules such as organic acids, alcohols, and polymer fragments.
However, faster degradation does not necessarily mean complete environmental safety. The researchers also identified the release of chemical additives, including antioxidants, stabilizers, and plasticizers. Some transformation products showed potential ecological toxicity in computational assessments, highlighting the need for further investigation.
The study provides valuable insights for developing environmentally responsible agricultural materials and improving assessments of biodegradable plastics in farmland.
"Understanding how biodegradable plastics interact with soil minerals can help us better predict their environmental fate and guide the development of safer agricultural materials," Liu added.
The researchers emphasize that further field studies are needed to examine long-term degradation, chemical migration, and ecological risks under natural agricultural conditions.
Ultimately, the findings demonstrate that the environmental performance of biodegradable plastics depends not only on the materials themselves, but also on the complex soil environments in which they are used.
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Journal reference: Liang C, Ji C, Feng F, Wang S, Liu G, et al. 2026. Enhanced degradation of biodegradable mulch films driven by interactions between clay minerals, UV light, and soil burial depth. New Contaminants 2: e027 doi: 10.48130/newcontam-0026-0024
https://www.maxapress.com/article/doi/10.48130/newcontam-0026-0024
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About the Journal:
New Contaminants (e-ISSN 3069-7603) is an open-access journal focusing on research related to emerging pollutants and their remediation.
