Department of Crop & Soil Sciences, Washington State University, Puyallup and Pullman, WA, USA.
Department of Biosystems Engineering and Soil Science, The University of Tennessee, Knoxville, TN, USA.
Water Res. 2023 Jul 1;239:120018. doi: 10.1016/j.watres.2023.120018. Epub 2023 May 2.
Plastic pollution caused by conventional plastics has promoted the development and use of biodegradable plastics. However, biodegradable plastics do not degrade readily in water; instead, they can generate micro- and nanoplastics. Compared to microplastics, nanoplastics are more likely to cause negative impacts to the aquatic environment due to their smaller size. The impacts of biodegradable nanoplastics highly depend on their aggregation behavior and colloidal stability, which still remain unknown. Here, we studied the aggregation kinetics of biodegradable nanoplastics made of polybutylene adipate co-terephthalate (PBAT) in NaCl and CaCl solutions as well as in natural waters before and after weathering. We further studied the effect of proteins on aggregation kinetics with both negative-charged bovine serum albumin (BSA) and positive-charged lysozyme (LSZ). For pristine PBAT nanoplastics (before weathering), Ca destabilized nanoplastic suspensions more aggressively than Na, with the critical coagulation concentration being 20 mM in CaCl vs 325 mM in NaCl. Both BSA and LSZ promoted the aggregation of pristine PBAT nanoplastics, and LSZ showed a more pronounced effect. However, no aggregation was observed for weathered PBAT nanoplastics under most experimental conditions. Further stability tests demonstrated that pristine PBAT nanoplastics aggregated substantially in seawater, but not in freshwater, and only slightly in soil pore water; while weathered PBAT nanoplastics remained stable in all natural waters. These results suggest that biodegradable nanoplastics, especially weathered biodegradable nanoplastics, are highly stable in the aquatic environment, even in the marine environment.
传统塑料造成的塑料污染推动了可生物降解塑料的发展和应用。然而，可生物降解塑料在水中不易降解，反而会产生微塑料和纳米塑料。与微塑料相比，纳米塑料由于其尺寸更小，更有可能对水生环境造成负面影响。可生物降解纳米塑料的影响高度依赖于其聚集行为和胶体稳定性，但这些仍然未知。在这里，我们研究了聚己二酸丁二醇酯共对苯二甲酸酯（PBAT）制成的可生物降解纳米塑料在 NaCl 和 CaCl 溶液以及风化前后天然水中的聚集动力学。我们进一步研究了带负电荷的牛血清白蛋白（BSA）和带正电荷的溶菌酶（LSZ）对聚集动力学的影响。对于原始 PBAT 纳米塑料（未风化），Ca 比 Na 更剧烈地使纳米塑料悬浮液失稳，在 CaCl 中的临界聚沉浓度为 20 mM，而在 NaCl 中为 325 mM。BSA 和 LSZ 都促进了原始 PBAT 纳米塑料的聚集，LSZ 的效果更为明显。然而，在大多数实验条件下，风化的 PBAT 纳米塑料没有发生聚集。进一步的稳定性测试表明，原始 PBAT 纳米塑料在海水中大量聚集，但在淡水中不会，在土壤孔隙水中仅略有聚集；而风化的 PBAT 纳米塑料在所有天然水中都保持稳定。这些结果表明，可生物降解纳米塑料，尤其是风化的可生物降解纳米塑料，在水生态环境中非常稳定，即使在海洋环境中也是如此。
