Modelling the spatial and seasonal distribution, fate and transport of floating plastics in tropical coastal waters.

A coupled high-resolution hydrodynamic-particle tracking model was developed to study the spatiotemporal distribution and pathways of floating plastics in the coastal waters of equatorial Singapore. The coupled model was first calibrated and validated against the field measurements and then applied to explore impact of various prevailing wind and hydrodynamic conditions on fate and transport of the plastics. The results highlighted that the wind effect on the hydrodynamics is negligible, but it influences the transmissions of floating plastics significantly in the Singapore's coastal waters. The spatial and seasonal hotspots of plastic waste were identified, which were consistent with field observations when the windage ranged from 3% to 5%. A further evaluation of the predicted trajectories showed that plastic wastes released from the land could be transported approximately 70 km seaward within 72 h when the windage was 5%. Furthermore, it was also found that the effects of climate change and increasing plastic usage would aggravate plastic pollution and accelerate its transport. The established model can provide new insights into the spatiotemporal distribution and fate of plastic waste in the tropical coastal waters, which is useful to assist regulators in making policy decisions in response to the future climate change and plastic usage.