Figure 3

(a) The relationship of Rouse number (Ro) and dimensionless microplastics velocity (\(U_{MPs}^{*}\)), with yellow highlighted dots (Re* > 15,000); (b) observations of PS-MPs’ movement/ settlement in vegetation zone (B2); and (c) observations of PS-MPs’ movement/ settlement in boulder zone (D5) (the motion of PS-MPs highlighted with the sequence of squares).