Entrainment and vertical mixing of aquatic microplastics in turbulent flow: The coupled role of particle size and density

• Published in: Marine pollution bulletin Vol. 184; p. 114160
• Main Authors: Shamskhany, Arefeh, Karimpour, Shooka
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-11-2022
• Subjects: Aquatic microplastics; Backward facing step; Particle entrainment; Particle size; Settling parameter; Turbulent flow; Aquatic microplastics; Particle entrainment; Particle size; Turbulent flow; Settling parameter; Backward facing step
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2022.114160

Diversity in microplastics' characteristics, including their size, affects their transport and distribution in aquatic systems. Furthermore, turbulent induced mixing is often considered dominant in the dispersion of sediments and contaminants in marine and freshwater systems, which is also affected by particle size. The aim of this study is to investigate the effect of microplastics' size and polymer density on their mixing behaviour in response to turbulent structures. Using sediment analogy, several parameters are defined to describe entrainment patterns of microplastic particles of common polymers. Our results indicate that the level of mixing of microplastics in turbulent flow can vary several orders of magnitude. While large particles' vertical motion may be dominated by gravitational settling or rising, the motion of fine microplastics is mainly governed by the ambient turbulent flow. Our findings provide a plausible explanation for the presence of fine microplastics in remote areas.
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•Aquatic microplastics (MPs) have complex characteristics affecting their distribution•Entrainment of different size MPs of common polymers was assessed in turbulent flow.•For a given shape, particle size, density, and flow intensity affect entrainment.•We demonstrated that entrainment level can vary significantly, depending on size.•In sizes of 100 and 200 μm, the density has a minimal effect on entrainment patterns.