Insights into the abiotic fragmentation of biodegradable mulches under accelerated weathering conditions

Biodegradable mulches (BMs) can be tilled into soils to mitigate disposal and environmental problems. However, the content of biodegradable microplastics (BMPs) would increase with the addition of biodegradable macro -plastics (BMaPs). The fragmented particles have a strong affinity to soil pollutants, having the potential to transfer via the terrestrial food web in an agroecosystem. Based on the spectral analysis and particle size analysis, this study explored the physicochemical characteristics of weathered BMaPs and BMP-derived dissolved organic matter (DOMBMP). Ultraviolet (UV) irradiation reduced the mechanical strength of BMaPs and induced oxygenated functional groups, thus increasing surface roughness and hydrophilicity. This promoted the adsorption of aromatic compounds and heavy metals from soils to BMPs. After entering the water environment, the pH of the solution with DOMBMP decreased, whereas the concentration of dissolved organic carbon (DOC) increased. Compared with paper mulch, bioplastic mulch contributed a higher amount of DOMBMP, such as ar-omatic structure-containing chemicals and carboxylic acids, to the water environment but released fewer and smaller plastic particles. The findings from this study can help manage environmental risks and determine disposal strategies after the use of mulching.

Automated summary

Biodegradable mulches (BMs) can help mitigate disposal and environmental problems, but the addition of biodegradable macro-plastics (BMaPs) can increase the content of biodegradable microplastics (BMPs). UV irradiation weakens BMaPs and increases their roughness and hydrophilicity, promoting the adsorption of soil pollutants. Compared to paper mulch, bioplastic mulch releases fewer and smaller plastic particles but contributes more dissolved organic matter with aromatic structures and carboxylic acids to the water environment.