Transport of micron-sized polyethylene particles in confined aquifer: Effects of size, ageing, and confining pressure

Abstract Contamination of groundwater by microplastics (MPs) is increasingly reported and draw growing attention due to their potential risks. To understand how MPs migrate into the groundwater, many previous works have investigated the transport of MPs using man-made microspheres of few microns or smaller as models. However, MPs observed in the environment are more diverse in size, shape, and types, which may have different migration behaviors. In this work, transport of irregular shaped polyethylene (PE) particles in sand packed column was studied. Small MPs (22-37 μm) generally have a high mobility than large MPs (44-74 μm) but can also be affected by aging. Ageing decreased the hydrophobicity of the MPs and increased their surface negative charge, which could have facilitated the transport of MPs. However, the physical barrier of space in the porous medium might have a greater influence on the transport of the MPs. The retention of the MPs was enhanced with the increase in pressure due to compression that decreased pore size. Results from this study showed that MPs of environmental features can also be transported in the groundwater but the processes could be governed by different factors from that of man-made plastic microspheres.