Non-targeted Analysis of Leachates from Mulch film Microplastics under UV Exposure

Abstract

Microplastics are increasingly accumulating in soil environments, with mulch films identified as a major source. However, limited information is available on the chemical compounds leached from these mulch film- derived microplastics into soil. In this study, compounds leached from PE mulch films (black and white) and biodegradable mulch films (PLA+PBAT) were analyzed under UV exposure, using water and ethanol as leaching solvents. Even though biodegradable mulch films are considered alternatives to conventional PE films, they exhibited a greater number of chemical features in their leachates. To identify the leached compounds, library matching and in-silico fragmentation integrated with a plastic-specific database were applied. Additionally, Molecular networking analysis was employed to visualize structurally related chemical features and predict potential transformation products formed under environmental conditions. As a result, 8 compounds were tentatively identified from the PE black film and 8 compounds from the PE white film, while 16 compounds were identified from the biodegradable film. UV exposure increased the chemical complexity of leachates from both PE and biodegradable films. Notably, 9-Octadecenamide, N,N-bis(2-hydroxyethyl)-, (9Z)-, a substance classified as hazardous, was detected only after UV exposure. These findings highlight the importance of including UV exposure conditions when assessing the chemical risks of plastic mulch films in soil environments. Furthermore, they underscore the need for systematic characterization of mulch film leachates to better understand their potential environmental impacts.