Aging Processes of Polyethylene Mulch Films and Preparation of Microplastics with Environmental Characteristics
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Aging Processes of Polyethylene Mulch Films and Preparation of Microplastics with Environmental Characteristics Ting Wang1 · Yini Ma1 · Rong Ji1 Received: 1 July 2020 / Accepted: 13 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this study, we explored the aging processes of a commercial polyethylene (PE) mulch film under UV irradiation and compared the laboratory aged films with films aged in nature. Overall, the aged films obtained from laboratory conditions were similar with that from natural conditions. Among the investigated factors, UV irradiation was crucial in the aging of the films, producing cracks and oxygen-containing functional groups on the films surface, constantly with natural aging. The formation of cracks induced a decrease of mechanical strength as well as the formation of MPs on the surface. The chemical oxidations detected by Fourier-transform infrared spectroscopy (FTIR) usually happened after the observed physical changes during aging. Moreover, a protocol was developed for laboratory preparation of MPs with characteristics similar with that from environmental aging and PE MPs with sizes of 2–400 μm could be produced in large amounts at relatively short period of time. Keywords Polyethylene · Mulch films · Aging · UV irradiation · Laboratory preparation · Microplastics Plastic films are widely used in modern agriculture systems as mulches covering the fields, for constructing greenhouses, and for preventing permeation and flooding in irrigation systems. The global plastic production reached approximately 348 million tons in 2017 (Plastics Europe 2017). In 2016, the use of agricultural plastic films in China reached 2.6 million tons, of which the use of mulch was 1.47 million tons, and the area covered by mulch was 18.4 million hectares (NBS 2017a). Both the usage and coverage of mulch films have increased year by year. Although these plastic mulch films could improve crop yields and help pest control, the low recycle rates of these films caused serious regional pollution of plastics residuals, posing environmental risks both above and belowground (Xu et al. 2018; Qi et al. 2020). Owing to a series of aging processes, such as light (especially UV), wind erosion, water erosion, acid attack, Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00128-020-02975-x) contains supplementary material, which is available to authorized users. * Yini Ma [email protected] 1
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China
microbial colonization, and even animal chewing (Duis and Coors 2016; Napper and Thompson 2019), residual mulch films are broken down or degraded into small-sized plastic fragments, and become the main source of microplastics (MPs,
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