Microplastics distribution, transport and potential risks in sediments across different functional areas of megacities: From storm sewer networks to urban river

Order to investigate the distribution and potential risks of microplastics (MPs) in sediments from different functional areas of megacity storm sewer networks, the abundance and characteristics of MPs in sediments from storm sewer manholes in five functional areas of Chengdu's storm sewer network were investigated, and the impacts of land use and environmental factors were also explored. The results showed that microplastic abundance varied in the range of 2641.5-10,566 items/kg dry weight, and the size trend showed that the main pipe area > residential area > green area > commercial area > educational area. The shapes of MPs in the sediments are, in order, fragments (37.32 %), films (27.46 %), fibers (22.12 %), and particles (13.1 %). MPs are rich in color, mostly colored, accounting for 88.36 %. The particle size is mainly concentrated in 50-200 mu m, accounting for 67.06 %. Stormwater catchment areas, traffic performance index for roads, and places with large populations exhibit higher amounts of MPs. The longer the building has been in use, the lower the number of MPs exhibited. The results of the PHI and RI analyses showed that the potential ecological risk is higher in the main pipe and commercial areas than in the other functional areas. This suggests the type of MPs contributes more to the potential risk than the abundance. The characteristics of MPs in storm sewer network sediments are highly similar to those in the subsoil of their receiving waters, suggesting that the storm sewer network is an important source of MPs in urban rivers.