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Plastic drift : Mapping the course of microplastic transport in turbulent riverine flows.
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Researchers investigated the transport dynamics of 24 negatively buoyant microplastic particles across a spectrum of sizes, shapes, and densities using a 3D particle tracking system in turbulent open channel flow, generating 720 trajectories. They found that particle shape was the dominant determinant of transport behavior, with fibers tending to remain near the water surface at lower forward velocities while spheres stayed closer to the bed with higher forward velocities.
Microplastics present significant challenges to aquatic ecosystems, yet there remains a limited comprehension of the mechanisms governing their transport. Insights from natural sediment dynamics present a promising approach to address this knowledge gap. The concept of the transport stage is central to sediment transport analysis, characterizing the relationship between fluid shear velocity and particle settling velocity. However, inherent variability in microplastics physical properties such as shape and density raise doubts regarding the applicability of conventional sediment transport models to microplastics. To confront this issue, we conducted laboratory experiments to investigate the trajectories of 24 negatively buoyant microplastic particles, encompassing a spectrum of sizes, shapes, and densities. Employing a 3D particle tracking system, we documented the particles' movement within turbulent open channel flow, generating a dataset of 720 trajectories for subsequent analysis. Our findings indicate a robust relationship between the transport stage and both the mean forward velocity and vertical positioning of microplastic particles within the water column. Notably, particle shape emerged as a pivotal determinant of transport dynamics. Fibers exhibited lower mean forward velocities with a tendency to remain near the water surface. On the contrary, spheres tended to remain closer to the bed while exhibiting higher mean forward velocity. Further analysis revealed distinct modes of transport akin to those observed in natural sediment dynamics, encompassing rolling/sliding, saltation, and suspension. Overall, our study revealed a correlation between the transport stage and the temporal distribution of microplastics across distinct modes of transport. Building upon these laboratory insights, we drew a novel phase diagram tailored specifically to microplastics, analogous to practice in sedimentology. This innovative framework offers a comprehensive depiction of microplastic transport phenomena, which could improve the performance of prediction models. By improving our understanding and prediction of microplastic transport, this work can facilitate targeted interventions to mitigate their environmental impact. Also see: https://micro2024.sciencesconf.org/558476/document
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Plastic drift : Mapping the course of microplastic transport in turbulent riverine flows.
AI summary Read the abstract
Researchers conducted laboratory experiments tracking the 3D trajectories of 24 negatively buoyant microplastic particles spanning a range of sizes, shapes, and densities in turbulent open channel flow, generating 720 trajectories to evaluate how well conventional sediment transport models apply to microplastics. Results revealed that the inherent variability in microplastic physical properties challenges direct application of sediment transport concepts to microplastic fate prediction in rivers.
Effect of Shape and Size on the Transport of Floating Particles on the Free Surface in a Natural Stream
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Researchers used particle tracking velocimetry to study how shape and size affect the movement of floating particles on the turbulent free surface of a natural stream, finding that millimeter-scale spheres behaved differently from centimeter-scale irregular objects. Understanding particle transport mechanics is essential for predicting microplastic fate in river systems.
Quantifying microplastic particle transport and retention in an experimental flume environment
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Researchers conducted flume experiments to quantify how microplastic particles of different shapes and densities are transported and retained in artificial river channels under controlled flow conditions. The results show that particle shape and flow dynamics strongly interact to determine where microplastics settle or remain suspended in river systems.
Effect of Shape and Size on the Transport of Floating Particles on the Free-surface of a Meandering Stream
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This study used particle tracking velocimetry to investigate how the shape and size of floating particles affect their transport on the turbulent free surface of a field-scale meandering stream, with direct relevance to predicting plastic pollution movement in rivers. Millimetre-sized spherical tracers were compared with centimetre-sized discs and rods at two locations with different turbulence levels. Results showed that particle shape and size influence lateral drift and dispersion, with implications for modeling how plastic particles of varied morphology are transported through natural waterways.
Mapping Microplastic Movement: A Phase Diagram to Predict Nonbuoyant Microplastic Modes of Transport at the Particle Scale
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Researchers tracked 24 different types of nonbuoyant microplastic particles in turbulent open channel flow to understand how they are transported in aquatic environments. They found that microplastics move similarly to natural sediments through rolling, saltation, and suspension, but particle shape strongly influences transport behavior, with fibers staying closer to the water surface than spheres. The study introduces a new phase diagram for predicting microplastic transport modes based on flow conditions and particle properties.
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