The Key Laboratory of Water and Sediment Sciences, Ministry of Education; State Environmental Protection Key Laboratory of All Material Fluxes in River Ecosystems; College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China.
Department of Ultrasound, Peking Union Medical College Hospital, Peking Union Medical College & Chinese Academy of Medical Sciences, PR China.
J Hazard Mater. 2021 Aug 5;415:125550. doi: 10.1016/j.jhazmat.2021.125550. Epub 2021 Mar 2.
Bacteria, biological colloids with wide presence in natural environments, would interact with plastic particles (emerging colloids with great concern recently) and thus would influence the fate and distribution of plastics in environment. In present research, the impacts of bacteria (both Gram (-) E. coli and Gram (+) B. subtilis) on the transport/deposition of model microplastics (MPs) in porous media were examined in NaCl salt solutions (5 and 25 mM, pH = 6). Both negative carboxylate-modified MPs (CMPs) and positive amine-modified MPs (AMPs) were concerned. We found that under both solution conditions, the presence of both types of bacteria decreased CMPs transport and enhanced retention of CMPs in sand columns. In contrast, the presence of bacteria (regardless of cell type) yet increased AMPs transport and decreased their deposition in sand columns under both ionic strength conditions. The mechanisms leading to the altered transport of CMPs and AMPs by bacteria were different. The formation of larger sized CMPs-bacteria clusters and the extra deposition sites resulted from bacteria adsorbed on quartz sand contributed to the decreased CMPs transport and enhanced their deposition in sand columns. Whereas, the formation of AMPs-bacteria clusters with overall negatively surface charge improved AMPs transport in quartz sand.
细菌是一种在自然环境中广泛存在的生物胶体，它们会与塑料颗粒（最近备受关注的新兴胶体）相互作用，从而影响塑料在环境中的归宿和分布。在本研究中，我们在 NaCl 盐溶液（5 和 25 mM，pH = 6）中考察了细菌（革兰氏阴性的大肠杆菌和革兰氏阳性的枯草芽孢杆菌）对模型微塑料（MPs）在多孔介质中迁移/沉积的影响。我们关注了带负电的羧基改性 MPs（CMPs）和带正电的胺基改性 MPs（AMPs）。结果发现，在这两种溶液条件下，两种类型的细菌都降低了 CMPs 的迁移，增强了 CMPs 在砂柱中的滞留。相比之下，在两种离子强度条件下，细菌的存在（无论细胞类型如何）都增加了 AMPs 的迁移，减少了它们在砂柱中的沉积。细菌导致 CMPs 和 AMPs 迁移变化的机制不同。细菌在石英砂上吸附导致 CMPs 形成更大尺寸的 CMPs-细菌团簇和额外的沉积位点，从而降低了 CMPs 的迁移并增强了它们在砂柱中的沉积。而带负电的 AMPs-细菌团簇的形成改善了 AMPs 在石英砂中的迁移。
