On the vertical structure of non-buoyant plastics in turbulent transport
Publication date
2024-02-13
Document type
Forschungsartikel
Author
Lofty, James
Valero, Daniel
Moreno-Rodenas, Antonio
Wilson, Catherine
Ouro, Pablo
Franca, Mário J.
Organisational unit
Publisher
Elsevier
Series or journal
Water Research
ISSN
Periodical volume
254
Article ID
121306
Part of the university bibliography
✅
Language
English
Abstract
Plastic pollution is overflowing in rivers. A limited understanding of the physics of plastic transport in rivers hinders monitoring, the prediction of plastic fate and restricts the implementation of effective mitigation strategies. This study investigates two unexplored aspects of plastic transport dynamics across the near-surface, suspended and bed load layers: (i) the complex settling behaviour of plastics and (ii) their influence on plastic transport in river-like flows. Through hundreds of settling tests and thousands of 3D reconstructed plastic transport experiments, our findings show that plastics exhibit unique settling patterns and orientations, due to their geometric anisotropy, revealing a multimodal distribution of settling velocities. In the transport experiments, particle-bed interactions enhanced mixing beyond what established turbulent transport theories (Rouse profile) could predict in low-turbulence conditions, which extends the bed load layer beyond the classic definition of the bed load layer thickness for natural sediments. We propose a new vertical structure of turbulent transport equation that considers the stochastic nature of heterogeneous negatively buoyant plastics and their singularities.
Description
Under a Creative Commons License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
Version
Published version
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