Microplastics rise rate under breaking waves*

Breaking waves play a major role in breakup and transport of marine microplastics. Understanding their transport under breaking waves is crucial for modeling and mitigating marine microplastics pollution. The experiment was carried out in a wind-wave facility with a test section of 6.0×0.4×0.6m³. The breaking wave generated turbulence is characterized using 2D particle image velocimetry. The background turbulence energy dissipation rate is ~1 m²s^-3 shortly after wave breaking and 10^-3 m²s^-3 60 seconds later. The rise rate statistics of spherical plastic particles with diameters ranging from 2 – 5 mm and specific gravity of 0.98 have been acquired by particle tracking velocimetry. The data analysis focuses on the effects of particle size and temporal evolution of turbulence level on particle rise rate. The results show a strong correlation between rise rate and the turbulence level, indicating the trajectory biasing plays a role in modifying their rise rate statistics. Our data provide valuable corrections to the rising rate of microplastics under breaking waves, offering experimental data support for understanding the transport characteristics and modeling of marine microplastics in breaking wave environments.