Particle size and co-presence of PFOA alter the transport of microplastics in saturated natural sediment

The transport of microplastics (MPs) with two different sizes in the absence and presence of perfluorooctanoic acid (PFOA) in sediment were systematically investigated in this study. Smaller size of MPs exhibited great transport mobility, while larger size of MPs significantly retained in sediment via electrostatic repulsion and straining mechanisms. MPs transport was insignificantly affected by influent pH values (4.7 and 6.0), likely due to the great buffer capacity of sediment. Effect of PFOA on MPs transport in sediment varied with MPs size and influent pH conditions. PFOA induced more negatively charged MPs surface and greater MPs transport at influent pH of 4.7, and this accelerating effect was more significant for MPs with greater size. In contrast, PFOA have little effect on the transport of both sized MPs at influent pH of 6.0. This work improved our understanding of MPs transport with the co-presence of PFOA in sediment environment.