New insights into the role of marine plastic-gels in microplastic transfer from water to the atmosphere via bubble bursting

The pervasiveness of microplastics (MPs) in global oceans is raising concerns about their adverse impacts on ecosystems. The mechanistic understanding of MP transport is critical for evaluating its fate, flux, and ecological risks specifically. Currently, bubble bursting is believed to represent an important route for MP transfer from sea surfaces to the atmosphere. However, the detailed mechanisms of the complex physico-chemical interactions between MPs, water composition, and gel particles in the air-sea interface remain unknown. Our results sug-gested three steps for MP transfer between air-sea phases: (1) MPs incorporating into gel aggregates in the water column; (2) further accumulation of plastic-gel aggregate in the surface layer phase; finally (3) ejection of ag-gregates from the sea when bubbles of trapped air rise to the surface and burst. The water composition (e.g., high salinity, gel concentration and viscosity) can modulate plastic-gel aggregation and subsequent transport from water to the atmosphere. The possible mechanism may be closely tied to the formation of plastic-gel via cation -linking bridges, thereby enhancing plastic-gel ejection into air. Collectively, this work offers unique insights into the role of marine plastic-gels in determining MP fate and transport, especially at air-sea interfaces. The data also provide a better understanding of the corresponding mechanism that may explain the fates of missing plastics in the ocean.

Automated summary

The widespread presence of microplastics in global oceans raises concerns about their negative impacts on ecosystems. Understanding the mechanistic transport of microplastics is crucial for evaluating their fate and ecological risks. This study suggests a three-step process for microplastic transfer between air and sea phases, involving the incorporation of microplastics into gel aggregates, accumulation of plastic-gel aggregates on the water surface, and ejection of aggregates when trapped air bubbles burst. The composition of water, such as salinity and gel concentration, can modulate the aggregation and transport of microplastics. This research provides valuable insights into the fate of microplastics in the ocean and their transport at air-sea interfaces.