Occurrence and migration patterns of microplastics in different tidal zones of tourist beaches: A case study in the Bohai Bay, North China

Coastal areas are acknowledged to be significant reservoirs of microplastics, while limited research on their presence and migration in the intertidal zones. This study investigated in a tourist beach in northern China, to reveal the occurrence of microplastics at different intertidal heights, elucidates their migration patterns, and discusses the impact of tourist activities on microplastics. Results showed that the mean microplastic abundance was 2114.8 ± 933.2 items/kg in sediments and 30,670.8 ± 15,094.9 items/m³ in seawater. Fibers were the most common shape; transparent, blue, green and black prevailed in color; and cellulose and PET were the most common components. Microplastic abundances decreased from high tide zone to low tide zone, and the abundances of microplastics in seawater were positively correlated with those in the high tide zone and negatively correlated with those in the low tide zone. Compared to wave disturbance, human activities have a relatively limited impact on microplastic abundance. However, intensive tourist activities contribute to a higher diversity of microplastic types on tourist beaches. This study enhances the understanding of the occurrence and migration patterns of microplastics in tourist beaches, and provides a valuable dataset and theoretical basis for subsequent research on microplastic pollution in coastal areas.