Department of Biosystems Engineering and Soil Science, University of Tennessee.
Department of Biosystems Engineering and Soil Science, University of Tennessee;
J Vis Exp. 2022 Jul 27(185). doi: 10.3791/64112.
Microplastics (MPs) and nanoplastics (NPs) dispersed in agricultural ecosystems can pose a severe threat to biota in soil and nearby waterways. In addition, chemicals such as pesticides adsorbed by NPs can harm soil organisms and potentially enter the food chain. In this context, agriculturally utilized plastics such as plastic mulch films contribute significantly to plastic pollution in agricultural ecosystems. However, most fundamental studies of fate and ecotoxicity employ idealized and poorly representative MP materials, such as polystyrene microspheres. Therefore, as described herein, we developed a lab-scale multi-step procedure to mechanically form representative MPs and NPs for such studies. The plastic material was prepared from commercially available plastic mulch films of polybutyrate adipate-co-terephthalate (PBAT) that were embrittled through either cryogenic treatment (CRYO) or environmental weathering (W), and from untreated PBAT pellets. The plastic materials were then treated by mechanical milling to form MPs with a size of 46-840 µm, mimicking the abrasion of plastic fragments by wind and mechanical machinery. The MPs were then sieved into several size fractions to enable further analysis. Finally, the 106 µm sieve fraction was subjected to wet grinding to generate NPs of 20-900 nm, a process that mimics the slow size reduction process for terrestrial MPs. The dimensions and the shape for MPs were determined through image analysis of stereomicrographs, and dynamic light scattering (DLS) was employed to assess particle size for NPs. MPs and NPs formed through this process possessed irregular shapes, which is in line with the geometric properties of MPs recovered from agricultural fields. Overall, this size reduction method proved efficient for forming MPs and NPs composed of biodegradable plastics such as polybutylene adipate-co-terephthalate (PBAT), representing mulch materials used for agricultural specialty crop production.
微塑料（MPs）和纳米塑料（NPs）分散在农业生态系统中会对土壤和附近水道中的生物区系构成严重威胁。此外，被 NPs 吸附的农药等化学物质会伤害土壤生物，并可能进入食物链。在这种情况下，农用塑料，如塑料覆盖膜，是农业生态系统中塑料污染的主要来源。然而，大多数关于命运和生态毒性的基础研究都使用理想化和代表性差的 MPs 材料，如聚苯乙烯微球。因此，如本文所述，我们开发了一种实验室规模的多步程序，用于机械形成代表性的 MPs 和 NPs 进行此类研究。塑料材料是由市售的聚丁二酸丁二醇酯-对苯二甲酸酯（PBAT）塑料覆盖膜制备的，这些塑料覆盖膜通过低温处理（CRYO）或环境风化（W）变脆，也可以使用未处理的 PBAT 颗粒。然后，通过机械粉碎对塑料材料进行处理，形成尺寸为 46-840 µm 的 MPs，模拟风与机械机械对塑料碎片的磨损。然后将 MPs 筛分成几个尺寸级分，以进行进一步分析。最后，将 106 µm 的筛分级分进行湿磨，生成 20-900 nm 的 NPs，这一过程模拟了陆地 MPs 的缓慢尺寸减小过程。通过立体显微镜的图像分析确定 MPs 的尺寸和形状，并用动态光散射（DLS）评估 NPs 的粒径。通过该过程形成的 MPs 和 NPs 具有不规则形状，这与从农业领域回收的 MPs 的几何特性一致。总的来说，这种尺寸减小方法对于形成由可生物降解塑料（如聚丁二酸丁二醇酯-对苯二甲酸酯（PBAT）组成的 MPs 和 NPs 非常有效，代表了用于农业特种作物生产的覆盖材料。
