Microplastics in urban stormwater sediments and runoff: An essential component in the microplastic cycle

Microplastics in urban stormwater is one of the main sources of microplastics in aquatic systems, however, has rarely been reviewed systematically. Microplastic abundance ranges for microplastics in stormwater and sediment was 0.02–15499 items/L and 106–109089 items/kg, respectively. The highest average (7740.45 ± 10901.54 items/L) was obtained for the mean microplastic concentrations found for the stormwater samples collected in Italy. Stormwater sediment samples analyzed in Sao Paulo, South Africa reported the highest abundance of 109089 items/kg. Although numerous microplastic morphologies were detected in stormwater and sediment, fibers/lines were the most common. Polyethylene microplastics most prevalently found in global stormwater systems. Black is the most abundant color found among stormwater microplastics. Majority of microplastics were ranged from 100 μm to 500 μm. This review present environmental fate and behavior of microplastics in urban stormwater runoff and suggested directions for future research regarding approaches to more robust abundance data through standardized microplastic extraction protocols.