Microplastics' shape impacts how far they travel in atmosphere: Study

WASHINGTON: A study found that Micron-sized microplastic waste can be carried across oceans and continents by the jet stream, and their shape influences how far they travel. A Cornell University team built a model to mimic the atmospheric transport of microplastic fibres, which demonstrates that flat fibres travel farther and are more frequent in the lower atmosphere than spherical fibres. Previous research suggested that these fibres were spherical.

The modelling has the potential to assist scientists in determining the sources of the ubiquitous trash, which might inform policy attempts to minimise it. The study was published in Nature Geoscience.

Microplastics in the atmosphere come from a variety of sources, including shredded tyres and road dust, as well as soda bottles floating in the ocean. If the plastic breaks down or is ground up, it can become small enough to be transported by the wind. Previous studies exaggerated the rate of deposition of flat fibres by characterising them as spherical or cylindrical in shape. When the fibres' flat structure is taken into account, they spend 450 per cent more time in the atmosphere than previously anticipated, allowing them to travel larger distances.

Furthermore, the modelling implies that the ocean may play a larger role than previously thought in directly generating microplastic particles into the atmosphere, according to Qi Li, assistant professor in the Department of Civil and Environmental Engineering and senior author of the paper. "We can now more accurately attribute the sources of microplastic particles that will eventually come to be transported to the air," she said. "If you know where they're coming from, then you can come up with a better management plan and policies or regulations to reduce the plastic waste. This could also have implications for any heavy particles that are transported in the lower atmosphere, like dust and pollen."

"I realized, with my postdoc, that the current global climate models have been assuming that the shape of these fibres are spheres," Li said. "We do not have, to date, a computationally feasible way of representing the settling velocity of these elongated fibres."