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Sinking rates of microplastics and potential implications of their alteration by physical, biological, and chemical factors

Marine Pollution Bulletin 2016 595 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Nicole Kowalski, Aurelia Reichardt, Joanna J Waniek

Summary

Researchers conducted sinking experiments with diverse microplastic particles and found that sinking velocity depends not only on density and size but also on particle shape, and that biofouling and weathering can substantially alter sinking rates with implications for how microplastics distribute through the water column.

To follow the pathways of microplastics in aquatic environments, profound knowledge about the behaviour of microplastics is necessary. Therefore, sinking experiments were conducted with diverse polymer particles using fluids with different salinity. Particles ranged from 0.3 and 3.6mm with sinking rates between 6 and 91×10(-3)ms(-1). The sinking velocity was not solely related to particle density, size and fluid density but also to the particles shape leading to considerable deviation from calculated theoretical values. Thus, experimental studies are indispensable to get basic knowledge about the sinking behaviour and to gain representative datasets for model approaches estimating the distribution of microplastics in aquatic systems. The sinking behaviour may be altered considerably by weathering and biofouling demanding further studies with aged and fouled plastic particles. Furthermore, assumptions are made about the influence of sinking fouled microplastics on the marine carbon pump by transferring organic carbon to deeper water depths.

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