Transport Characteristics of Polyethylene Microplastics in Porous Media Before and After Aging

Soil is a significant long-term reservoir for microplastics (MPs), with the annual amount of MPs released into soil far exceeding that released into the ocean. MPs entering the soil gradually undergo aging under the combined influence of physical, chemical, and biological factors, thereby affecting their environmental behavior. In this study, saturated quartz sand was used as a porous medium to investigate the effects of different environmental factors on the transport behavior of polyethylene microplastics (PE-MPs). The results show that the blocking effect caused a decrease in the transport ability of PE as its concentration increased, while flow shear stress led to an increase in transport ability as flow velocity increased. pH and ionic strength had little effect on the transport ability of aged PE, primarily due to the increase in surface roughness caused by aging, which affected the migration process. The presence of fulvic acid (FA) significantly enhanced the transport ability of PE, which was related to the increase in surface negative charge, thereby raising the risk of soil MPs contaminating groundwater.