The application of agricultural plastic products such as mulch, greenhouse covers, and silage films is increasing due to their economic benefits in providing an early and better-quality harvest. However, mechanical abrasion of these plastic materials by soil particles could result in generation of microplastic (MP) pollutants that could harm soil organisms and impact food safety. This study aims to better understand the physicochemical mechanisms resulting in the fragmentation of low-density polyethylene (LDPE). Herein, we used pellets and films to study the impacts of abrasive wear forces on their surface morphology variations and fragmentation behavior. An innovative laboratory approach was developed to abrade the plastic surface under controlled normal loadings and abrasion durations. The investigation of the plastics’ surface morphology variations due to the abrasion process revealed microcutting as the dominant process at low normal force (4 N). However, a combination of microploughing and microcutting occurred for new LDPE films by increasing the normal force to 8 N. Despite the significant surface morphology variations of the new LDPE film due to the abrasion process; the water contact angle did not alter. Furthermore, the fragmentation behavior of photodegraded LDPE pellets and films was compared to the new plastics. The extent of MPs (3 µm < d_p < 162 µm) generation due to fragmentation was studied using fluorescence microscopy imaging. The localized stress and strains at the contact sites of plastic and sand particles resulted in abrasion of the plastic surface. According to the results, the normal loadings and duration of abrasion played a significant role in the degree of fragmentation of plastics. Increasing the normal loading applied during the abrasion process from 2 to 8 N linearly increased the number of generated plastic fragments by more than five times for pellets and more than three times for film. Photodegradation significantly enhanced the extent of MPs fragmentation. Moreover, the limitations of this study and the implications for agricultural soil health were discussed.

中文翻译：

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深入了解机械磨损力下塑料破碎的机制：对农业土壤健康的影响

农用塑料产品（例如覆盖物、温室覆盖物和青贮薄膜）的应用正在增加，因为它们可以提供早期和更高质量的收成的经济效益。然而，土壤颗粒对这些塑料材料的机械磨损可能会导致微塑料（MP）污染物的产生，从而损害土壤生物并影响食品安全。本研究旨在更好地了解导致低密度聚乙烯（LDPE）碎裂的物理化学机制。在这里，我们使用颗粒和薄膜来研究磨料磨损力对其表面形态变化和破碎行为的影响。开发了一种创新的实验室方法，在受控的正常载荷和磨损持续时间下磨损塑料表面。对磨损过程引起的塑料表面形态变化的研究表明，微切削是低法向力 (4 N) 下的主要过程。然而，通过将法向力增加到 8 N，新型 LDPE 薄膜发生了微犁耕和微切削的组合。尽管由于磨损过程，新型 LDPE 薄膜的表面形态发生了显着的变化；水接触角没有改变。此外，还将光降解 LDPE 颗粒和薄膜的破碎行为与新型塑料进行了比较。MP 的范围 (3 µm < 尽管由于磨损过程，新型 LDPE 薄膜的表面形态发生了显着变化；水接触角没有改变。此外，还将光降解 LDPE 颗粒和薄膜的破碎行为与新型塑料进行了比较。MP 的范围 (3 µm < 尽管由于磨损过程，新型 LDPE 薄膜的表面形态发生了显着变化；水接触角没有改变。此外，还将光降解 LDPE 颗粒和薄膜的破碎行为与新型塑料进行了比较。MP 的范围 (3 µm <  使用荧光显微镜成像研究了由于碎裂而产生的d _{p < 162 µm）。}塑料和沙粒接触部位的局部应力和应变导致塑料表面磨损。结果表明，正常载荷和磨损持续时间对塑料的破碎程度起着重要作用。将磨损过程中施加的正常载荷从 2 N 增加到 8 N，产生的塑料碎片数量线性增加，对于颗粒来说增加了五倍以上，对于薄膜来说增加了三倍以上。光降解显着增强了 MP 的破碎程度。此外，还讨论了这项研究的局限性以及对农业土壤健康的影响。