Intertidal zone effects on Occurrence, fate and potential risks of microplastics with perspectives under COVID-19 pandemic

Micro-(nano-)plastics have become emerging contaminants worldwide in recent years. However, there has not been a critical review on their fate and potential risk in intertidal zones with different geological conditions. Thus, this review provides a comprehensive analysis of the roles of intertidal zones in accumulation or transportation of microplastics (MPs), involving convergence, migration, plastiglomerate, and ingestion effects. It is found that MPs are likely to be stranded in mudflats but be transported across the sandy beaches according to their intrinsic and external conditions. Meanwhile, MPs could also form the contamination of plastiglomerate and act as vectors for contaminants, even pathogens, in rocky and biological beaches. Thus, MPs together with nanoplastics (NPs) could potentially threaten the ecosystems of the intertidal zone by their ingestion and translocation. In view of the upsurge of personal protective equipment (PPE) during COVID-19, the occurrence of discarded PPE in the intertidal zones has also been summarized and discussed. Despite that the amount of discarded PPE is relatively smaller than other MPs, the pollution caused by these wastes could increase the possibility for pathogen-attached MPs becoming the source for spreading disease among wildlife and humans. It will be of vital importance for understanding the roles of intertidal zone in influencing the fate and ecotoxicity of the MPs. Moreover, the in-depth discussion on fate of the PPE in every type of intertidal zones can be conducive to drawing more attentions on plastic concerns in COVID-19 pandemic and achieving environmental sustainability.