Transport of Microplastics in Shore Substrates over Tidal Cycles: Roles of Polymer Characteristics and Environmental Factors

Tidal zones providing habitats are particularly vulnerableto microplastic (MP) pollution. In this study, the effects of tidal cycles onthe transport of MPs (4-6 mu m polyethylene, PE1; 125 mu m polyethylene,PE2; and 5-6 mu m polytetrafluoroethylene, PFTE) in porous mediacombined with various environmental and MPs properties weresystemically investigated. The results indicated that smaller substratesizes exhibited higher retention percentages compared to those of largersubstrate sizes under different tidal cycles. In terms of the size of MPs, alarger size (same density) was found to result in enhanced retention ofMPs in the column. As the number of tidal cycles increased, although thetransport of MPs from the substrate to the water phase was enhanced,PE1 was washed out more with the change in water level, compared toPTFE. Additionally, more MPs were retained in the column with theincrease of salinity and the decrease offlow velocity under the same tidalcycles. Ultraviolet and seawater aged PE1 showed enhanced transport, while aged PTFE showed enhanced retention under the sametidal cycles. These results can help understand the MP behaviors in the shoreline environment and provide support for future cleanup and sampling in tidal zones