Aggregation and Deposition Kinetics of Polystyrene Microplastics and Nanoplastics in Aquatic Environment

Microplastics (MPs) and nanoplastics (NPs) attract widespread attention due to their final threats to human health. Here, 50 nm and 500 nm polystyrene particles (PS50 and PS500) were selected as the typical NPs and MPs, respectively. Their aggregation kinetics was monitored, and their deposition was investigated on silica and alumina surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D). PS500 has higher critical coagulation concentration (CCC) values than PS50, because of the weaker Brownian diffusion, less particle number and lower collision chance. PS50 has smaller values of critical deposition concentration (CDC) than PS500, indicating the stronger adsorption on silica. Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations explain that PS500 has weaker attachment on silica and slower deposition rate on alumina than PS50. Our results demonstrate that solution chemistry, particle size and mineral surfaces determine the transport and distribution of plastic particles together.