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Settling behaviors of microplastic disks in water

Marine Pollution Bulletin 2023 14 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Yang Ge, Yang Ge, Zijian Yu, Abul B. M. Baki, Weiwei Yao, Matthew S. Ross, Wanqing Chi, Wenming Zhang

Summary

Researchers investigated the settling behavior of microplastic disk particles in water, finding that lighter disks sink in straight vertical paths while denser disks follow oscillating zigzag trajectories — differences that significantly influence microplastic transport and distribution in aquatic environments.

Microplastic (MP) disks have not been studied for settling behaviors in aquatic environments, which affects the transport and fate of MPs. Therefore, settling experiments were conducted on MP disks of three shapes and four common-seen materials. Lighter MP disks (with density ρ = 1.038 g/cm and length l ≤ 5 mm) followed rectilinear vertical trajectories, while heavier MP disks (ρ = 1.161-1.343 g/cm and l = 5 mm) followed zigzag trajectories with oscillations and rotations. The mean terminal settling velocities of MP disks were 19.6-48.8 mm/s. Instantaneous settling velocities of heavier MP disks fluctuated. Existing formulas could not accurately predict the settling velocity of MP disks; thus, a new model was proposed with an error of 15.5 %. Finally, the Re - I* diagram (Re is the disk Reynolds number and I* is the dimensionless moment of inertia) was extended for MP disks to predict settling trajectories.

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