Sedimentation of Irregular Shaped Microplastics Under Steady and Dynamic Flow Conditions

Because of different compositions, physicochemical properties and shapes in nature of the microplastics (MPs), their migration process in the environment is very different, which makes it difficult to predict the behavior trajectory. This article mainly studies the sedimentation law of MPs under static and dynamic water conditions. Four kinds of materials, respectively polystyrene (PS), Polyamide (PA), polyethylene terephthalate (PET) and polyvinyl chloride (PVC), about 1230 MP particles with irregular shapes are selected for sedimentation experiments. They are divided into three shapes: near-sphere, polygonal ellipsoid and fragment. The experimental results show that the near-sphere MPs settled at the fastest rate, followed by the polygonal ellipsoid MPs, and the fragmented MPs settled at the slowest rate. By the force analysis of MPs in the settlement process, and the theoretical formula of MP settlement rate with their shape, particle size, density and water density are obtained, which has better fitting degree.