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Article Tier 2

Reply on RC1

Researchers measured the gravitational settling velocities of commercially available glitter particles and synthetic fibres in air to better characterise atmospheric microplastic transport. They found glitters and fibres settled up to 74% and 78% slower than volume-equivalent spheres, respectively, indicating that non-spherical shapes substantially extend atmospheric residence times.

2025
Article Tier 2

The atmospheric settling of commercially sold microplastics

Researchers measured the gravitational settling velocities of commercially available glitter microplastics (0.1-3 mm nominal diameter) and synthetic fibers (1.2-5 mm length) in air, finding that non-spherical shapes cause complex settling behaviors that deviate substantially from spherical particle models used in atmospheric transport models.

2025
Article Tier 2

Atmospheric transport of microplastic particles as a function of their size and shape

Researchers investigated the atmospheric transport and settling of microplastic particles as a function of size and shape, implementing a shape-correction parameterization for fiber-shaped particles in an atmospheric transport model to better represent their reduced gravitational settling velocity compared to spheres. The study showed that non-spherical fibers experience greater atmospheric drag, increasing their residence time and transport distance, and that including shape effects improved agreement between model output and ground-based measurements.

2022
Article Tier 2

Gravitational settling of microplastic fibers: experimental results and implications for global transport

This study measured the gravitational settling velocities of microplastic fibers and found that their non-spherical shape causes them to settle much more slowly than spheres of the same volume. Current atmospheric transport models that assume spherical particles significantly underestimate how long fibers remain airborne. These results have important implications for predicting how far microplastic fibers can travel before depositing.

2023
Article Tier 2

Effects of Shape and Size on Microplastic Atmospheric Settling Velocity

Researchers measured atmospheric settling and horizontal drift velocities of various microplastic shapes and sizes in controlled settling chambers, providing empirical data needed to improve atmospheric transport models that explain how microplastics reach remote environments.

2023 Environmental Science & Technology 39 citations
Article Tier 2

Reply on RC2

Researchers presented advances in FLEXPART, a Lagrangian particle dispersion model, including improvements in trajectory accuracy by using native ECMWF vertical coordinates, enhanced gravitational settling calculations that account for non-spherical particle shapes such as microplastic fibers, and a revised wet deposition scheme. These updates achieved an 8-10% reduction in conservation errors for semi-conserved quantities and increased simulation accuracy for atmospheric transport of microplastic particles.

2024
Article Tier 2

Reply on CC1

This study examined the settling behavior of commercially available microplastic particles in the atmosphere, focusing on how physical properties such as size and shape influence transport and deposition, with implications for understanding the atmospheric dispersion of microplastics. The work responds to prior commentary by providing additional experimental data relevant to modeling large microplastic settling dynamics.

2025
Article Tier 2

Comment on egusphere-2025-605

Researchers examined the atmospheric settling behavior of commercially available glitter particles and synthetic fibers with complex non-spherical shapes to improve models of large microplastic transport and deposition. Experimental measurements of gravitational settling velocity for glitters (0.1-3 mm diameter) and fibers (1.2-5 mm length) provided data largely absent from prior literature on aerodynamic microplastic behavior.

2025
Article Tier 2

Reply on RC1

Researchers presented advances in FLEXPART, a Lagrangian particle dispersion model, including improvements in trajectory accuracy by using native ECMWF vertical coordinates, enhanced gravitational settling calculations that account for non-spherical particle shapes such as microplastic fibers, and a revised wet deposition scheme. These updates achieved an 8-10% reduction in conservation errors for semi-conserved quantities and increased simulation accuracy for atmospheric transport of microplastic particles.

2024
Article Tier 2

Long-distance atmospheric transport of microplastic fibers depends on their shapes

Researchers developed a theory-based settling velocity model for microplastic fibers in the atmosphere that accounts for fiber shape and cross-sectional dimensions, finding that correctly characterising flat fibers rather than treating them as cylinders increases estimated mean atmospheric residence time by over 450%, suggesting the ocean is a major source of airborne plastic and that long-range transport is far more efficient than previously thought.

2023 5 citations
Article Tier 2

Low Reynolds Number Settling of Cylindrical Rods with Various Geometries in a Quiescent Fluid

Researchers experimentally investigated the settling behaviour of curved, V-shaped, U-shaped, and S-shaped cylindrical rods at low Reynolds numbers to improve models of atmospheric microplastic fibre transport, conducting experiments with millimeter-scale metal rods spanning aspect ratios from 10 to 120. The study found that fibre geometry significantly affects settling trajectories and drag compared to simplified sphere or straight-cylinder approximations used in current atmospheric transport models.

2025 York University Digital Library (York University)
Article Tier 2

Reply on RC3

Researchers presented advances in FLEXPART, a Lagrangian particle dispersion model, including improvements in trajectory accuracy by using native ECMWF vertical coordinates, enhanced gravitational settling calculations that account for non-spherical particle shapes such as microplastic fibers, and a revised wet deposition scheme. These updates achieved an 8-10% reduction in conservation errors for semi-conserved quantities and increased simulation accuracy for atmospheric transport of microplastic particles.

2024
Article Tier 2

Modeling the Gravitational Settling of Microplastic Fibers in the Atmosphere

Researchers developed and applied a model for gravitational settling of microplastic fibers in the atmosphere, examining how fiber shape and size influence atmospheric residence time and deposition patterns to better understand the global atmospheric transport cycle of microplastics.

2022 Digital Commons - USU (Utah State University)
Article Tier 2

A physics-based and orientation-aware method for the direct calculation of  the settling speed of prolate spheroidal particles in the atmosphere : theoretical basis and comparison to laboratory and CFL data

Researchers developed a physics-based, orientation-aware method for calculating the settling speed of prolate spheroidal particles such as microplastic fibres in the atmosphere, grounding the approach in theoretical drag and orientation models rather than purely empirical fits and validating it against laboratory and CFD data.

2025
Article Tier 2

Terminal Settling Velocity of Cylindrical Rods with Various Geometries Applicable to Atmospheric Microplastics

Researchers measured how the shape of cylindrical microplastic fibers affects their settling speed through air, finding that curved and V-shaped fibers fall significantly faster than straight ones — up to 57% faster for V-shaped rods — which matters for predicting how airborne microplastics disperse in the atmosphere.

2024 Proceedings of the ... International Conference on Fluid Flow, Heat and Mass Transfer
Article Tier 2

Shape matters: long-range transport of microplastic fibers in the atmosphere

This study modeled the long-range atmospheric transport of microplastic fibers, finding that their elongated non-spherical shape causes them to travel much farther than spherical particles before settling. This helps explain why microplastic fibers are found even in the most remote locations on Earth, far from any plastic pollution source.

2023 arXiv (Cornell University) 2 citations
Article Tier 2

Modeling Microplastic Transport in the Marine Environment: Testing Empirical Models of Particle Terminal Sinking Velocity for Irregularly Shaped Particles

Researchers tested multiple drag models for predicting the terminal settling velocity of irregularly shaped microplastic particles in seawater, identifying three high-precision models and demonstrating that settling velocity is largely stable across ocean depths and independent of initial particle velocity, improving the accuracy of marine microplastic transport simulations.

2023 ACS ES&T Water 12 citations
Article Tier 2

Microplastic shape affects travel distance

Researchers found that microplastic shape significantly influences atmospheric transport distance, with fibre and complex-shaped particles travelling farther than spherical ones assumed in most models, helping explain the detection of microplastics in remote locations such as Antarctica and Mount Fuji.

2024 C&EN Global Enterprise
Article Tier 2

Modelling the effect of shape on atmospheric microplastic transport

Using atmospheric transport modeling, researchers showed that the shape of microplastic particles significantly affects how far they travel through the air. Long fibers can spread over a 32% larger area than spherical particles of the same size, and shape matters most for particles larger than 6 micrometers. Since particles in the 6 to 10 micrometer range can reach deep into human lungs, accurately accounting for shape is important for predicting where airborne microplastics end up and who might be breathing them in.

2024 Atmospheric Environment 25 citations
Article Tier 2

Towards better predicting the settling velocity of film-shaped microplastics based on experiment and simulation data

Researchers combined experimental and simulation data to better predict how film-shaped microplastics settle through water, since most existing models are based on spherical particles. They found that the particle definition approach was more suitable than equivalent spherical diameter for characterizing flat, irregular microplastics. The improved settling velocity predictions could help scientists better understand how film-shaped microplastics travel and accumulate in aquatic environments.

2024 Marine Pollution Bulletin 10 citations
Article Tier 2

Lagrangian tracking of particles settling through the atmosphere: influence of particle shape on its dispersion

Researchers launched instrumented balloon experiments as part of the IMPACT field campaign in northern Finland to track non-spherical particle settling through the atmosphere, finding that particle shape significantly influences dispersion trajectories and that existing spherical-particle models underestimate the spread of realistic atmospheric particles such as microplastics.

2025
Article Tier 2

Improved Settling Velocity for Microplastic Fibers: A New Shape-Dependent Drag Model

A new shape-dependent drag model was developed to improve the accuracy of settling velocity predictions for microplastic fibers, addressing a major limitation of existing drag models that significantly underpredict fiber settling in aquatic environments.

2021 Environmental Science & Technology 85 citations
Article Tier 2

Settling velocity of microplastic particles having regular and irregular shapes

Researchers measured how quickly microplastic particles of various shapes settle through water, testing 66 different particle types including spheres, cylinders, fibers, and irregular fragments. They found that particle shape significantly affects settling speed, with fibers and flat shapes sinking more slowly than spheres of the same size. The study provides new equations for predicting where microplastics end up in oceans and waterways based on their shape.

2023 Environmental Research 86 citations
Article Tier 2

Comment on egusphere-2025-605

Researchers examined the atmospheric transport of microplastics, focusing on how their settling behavior — determined by physical properties including size and shape — governs the dispersion of large microplastic particles through the atmosphere and their deposition across environments.

2025