Investigate the influence of microplastics weathering on their heavy metals uptake in stormwater

Plastic debris as the main portion of urban litters could be transported via storm runoff to the water resources. In this study the influence of microplastics (MPs) weathering on their Pb2+ and Zn2+ uptake in stormwater was examined. Low-density polyethylene (LDPE) and polyethylene terephthalate (PET) MPs were subjected to weathering through mechanical interaction with a mixture of silt/sand, and in synthetic stormwater. The surface analysis revealed significant physio-chemistry alterations of LDPE MPs due to the silt/sand weathering. However, this weathering mostly resulted in the surface morphology alterations of PET MPs. The kinetics of heavy metals adsorptions onto the new and stormwater weathered LDPE MPs were best described by pseudo 1st and 2nd models, respectively. Despite increasing Pb2+ uptake by weathered PET MPs, Zn2+ uptake by both new and weathered PET MPs was below the detection limit. Both Pb2+ and Zn2+ were released from new and silt/sand weathered LDPE MPs during five days exposure to the synthetic stormwater. This study underscores the critical role of plastic type and weathering conditions on heavy metal transport by MPs from the urban environment to the water resources