Shape Matters: Long-Range Transport of Microplastic Fibers in the Atmosphere

Area of Science:

• Environmental Science
• Atmospheric Science
• Materials Science

Background:

• Airborne microplastics are found globally, but atmospheric transport models struggle to predict their deposition accurately.
• Current models often simplify microplastic shapes, typically as spheres, neglecting their non-spherical nature which affects atmospheric behavior.

Purpose of the Study:

• To investigate the impact of microplastic fiber shape on gravitational settling velocities.
• To improve atmospheric transport models for microplastics by incorporating realistic particle shapes.
• To assess the potential long-range transport and stratospheric impacts of microplastic fibers.

Main Methods:

• Laboratory experiments measuring the gravitational settling velocities of microplastic fibers in air.
• Development and application of an atmospheric transport model using experimentally derived settling data.
• Simulation of microplastic fiber transport from populated areas to remote regions and the stratosphere.

Main Results:

• Microplastic fiber settling velocities were reduced by up to 76% compared to spheres of equivalent volume.
• Shape-corrected settling velocities significantly increased predicted horizontal and vertical atmospheric transport distances.
• Model results indicate that 1 mm microplastic fibers can reach remote regions like the Arctic, and smaller fibers can enter the stratosphere.

Conclusions:

• The non-spherical shape of microplastic fibers is critical for understanding their atmospheric transport and deposition.
• Microplastic fibers pose a greater risk for long-range transport to pristine environments compared to spherical particles.
• Stratospheric transport of microplastic fibers could lead to ozone depletion, highlighting the environmental threat of increasing plastic emissions.