The atmosphere, like the land and the water, is polluted by a variety of contaminants. Micron-sized microplastic trash that can be carried by the jet stream across oceans and continents has been detected in recent years.
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A team at Cornell has created a model to mimic the atmospheric movement of microplastic fibers and discovered that the shape of the fibers affects their velocity significantly. The research reveals that flat fibers are more common and travel farther in the lower atmosphere, contrary to earlier studies’ assumption that these fibers are spherical.
Scientists could be able to identify the sources of the ubiquitous waste with the use of modeling, which might guide attempts to eliminate it through policy.
The team’s study was published on September 25th, 2023 in Nature Geoscience under the title “Long-Distance Atmospheric Transport of Microplastic Fibres Influenced by Their Shapes.” Shuolin Xiao, a former postdoctoral researcher, is the lead author.
Road dust, broken tires, and even soda bottles floating in the sea are some of the many things that contribute to atmospheric microplastics. There is a chance that the plastic will break down or get so small that the wind can carry it.
The initiative started when Natalie Mahowald, the Irving Porter Church Professor in Engineering, was contacted by Qi Li, an assistant professor in Cornell Engineering’s Department of Civil and Environmental Engineering and the senior author of the publication. Li’s group studies hydrology and environmental fluid mechanics, mostly as they apply to Earth’s lower atmosphere.
Mahowald and co-author Janice Brahney of Utah State University recently researched the movement of airborne microplastics, which piqued Li’s interest. Li also spoke with Donald Koch, an expert in the fundamental fluid dynamics of fiber settling in turbulence and professor at the Smith School of Chemical and Biomolecular Engineering.
I realized, with my postdoc, that the current global climate models have been assuming that the shape of these fibers are spheres. We do not have, to date, a computationally feasible way of representing the settling velocity of these elongated fibers.
Qi Li, Assistant Professor, Department of Civil and Environmental Engineering, Cornell University
Li and Xiao set out to establish a more rigorous system of analysis by fusing the vast measurement data Mahowald and Brahney had gathered with Koch’s theoretical findings.
Two important conclusions emerged from this study, which led to the development of a theory-based settling velocity model that could incorporate large-scale climate models. Essentially, earlier research had exaggerated the rate of deposition of flat fibers by considering them to be spherical or cylindrical in shape. Because of their flat design, the fibers go farther and spend 450% more time in the atmosphere than previously thought.
Additionally, the researchers discovered that the bulk of the microplastic particles Mahowald and Brahney had gathered were flat fibers.
According to Li, the simulation also implies that the ocean may play a larger role in directly generating microplastic aerosols into the atmosphere than previously thought.
Li added, “We can now more accurately attribute the sources of microplastic particles that will eventually come to be transported to the air. If you know where they are coming from, then you can come up with a better management plan and policies or regulations to reduce plastic waste. This could also have implications for any heavy particles that are transported in the lower atmosphere, like dust and pollen.”
Yuanfeng Cui, a doctoral student, was a co-author.
The National Center for Atmospheric Research supplied computational resources for the study, which was funded by the National Science Foundation.
Xiao, S., et al. (2023) Long-Distance Atmospheric Transport of Microplastic Fibres Influenced by Their Shapes. Nature Geoscience. doi:10.1038/s41561-023-01264-6