Soil-biodegradable plastic films do not decompose in a lake sediment over 9 months of incubation

Abstract. Agriculture relies heavily on the use of plastic mulch films, which increase crop yields and lower water demands. Research has shown that agricultural mulch film may be transported to aquatic environments. We tested the mineralization of soil-biodegradable agricultural mulch films in freshwater lake sediments. Two types of commercial soil-biodegradable mulch films were incubated within lake sediment cores, and the production of CO₂ and CH₄ was followed over time. After the 40-week incubation period, films were visually intact and showed no signs of mineralization. Gas analyses showed no additional production of either CO₂ or CH₄ in the degradable film incubations, compared to control or PE plastic incubations. We conclude that the tested soil-biodegradable mulch films have a low biodegradability in lake sediments, likely reflecting that the lake sediment lacks active microbial degraders. Our results highlight the importance of preventing transport of soil-biodegradable mulch films from agricultural soils to surrounding aquatic environments.