Experimental study on transport and retention dynamics of macroplastics in gully pots

Plastic wastes sourced from urban areas can be retained and transported by urban drainage systems. However, comprehensive research on the transport of plastics in these systems is still required. This study examines the efficiency of gully pots in trapping macroplastics during rainfall events of different intensity, focusing on the influence of flow conditions, plastic types and the presence of sediments. Using a 1:1 scale gully pot model, with water flow ranging from 0.2 to 2.0 l/s we measured the transport and retention of bottles, caps, cigarette filters, and snack wrappings. The results revealed that high discharges significantly reduce plastic removal efficiency –i.e., less plastics remain trapped in the gully pot—, while sediments accelerate plastic transport, especially at high discharges. The study highlights the role of urban drainage systems to mitigate plastic pollution in aquatic environments.