Monitoring the Environmental Degradation of Biodegradable Mulch Films Using Py-GC-MS and a Multitechnique Analytical Approach

Abstract

Biodegradable mulch films have been developed for use in agriculture to reduce costs incurred during the retrieval of conventional mulch films and to prevent plastic pollution of soil caused by their incomplete removal. However, there are knowledge gaps on their degradation rate and potential environmental impact of any residuals. This study investigated the degradation of three commercially available mulch films, one made of polyethylene and two labeled as “biodegradable”. These products were exposed to four conditions in the open environment. After 24 months in soil, air, and a combination of air pre-exposure for 3 months followed by soil burial, all samples retained their overall film structure and were still recoverable, although different levels of physical and chemical changes indicated ongoing degradation. In seawater, no residual fragments of the biodegradable mulch films remained after 3 months of exposure. Pyrolysis-gas chromatography-mass spectrometry detected leaching of a plasticizer from one of the biodegradable films in all environments and other degradation features. The outcome of this study highlights the potential for environmental accumulation of mulch films labeled as “biodegradable” and the need for the development of international environmental testing standards and associated labeling to guide users on appropriate use and disposal of mulch films.