A recent study by scientists at the University of Vienna and the Max Planck Institute for Dynamics and Self-Organisation in Göttingen, has determined how far microplastic fibres travel in the atmosphere depends on particle shape.
While spherical particles settle quickly, microplastic fibres might travel as far as the stratosphere. The researchers first determined experimentally how fast microplastic fibres settle in the atmosphere and found that fibres settle substantially slower than spheres of the same mass.
In their study, the researchers argue that further studies are urgently needed to investigate the possible influence of microplastics on the atmosphere.
The research, ‘Shape Matters: Long-Range Transport of Microplastics in the Atmosphere,’ is published in Environmental Science & Technology.
A lack of data on microplastic fibres in the air
Mohsen Bagheri of the Max Planck Institute for Dynamics and Self-Organisation, who oversaw the laboratory experiments, commented: “Surprisingly, there is almost no data in the literature on the dynamics of microplastic fibres as they settle in the air.
“This lack of data is mainly due to the challenges of conducting controlled and repeatable experiments on such small particles in air.
Bagheri added: “With advances in submicron-resolution 3D printing and the development of a novel experimental setup that allows tracking individual microplastics in the air, we were able to fill this knowledge gap and improve existing models in this study.”
The researchers then implemented a model describing the settling process of non-spherical particles into a global atmospheric transport model.
The differences to spherical particles were dramatic: fibres with lengths of up to 1.5 mm could reach Earth’s most remote places in the model, while the model showed that spheres of the same mass settled much closer to the plastic source regions.
“With the novel laboratory experiments and modelling analysis, we certainly reduce uncertainties about the atmospheric transport of microplastic fibres and can finally explain via modelling why microplastics reach very remote regions of the planet,” explained Daria Tatsii from the Department of Meteorology and Geophysics at the University of Vienna and first author of the study.
“An important result of the study is that our analysis applies not only to microplastics but also to any other particles such as volcanic ash, mineral dust, pollen, etc.”
These harmful fibres could reach as far as the stratosphere
The researchers also found that plastic fibres could reach much greater heights in the atmosphere than spheres of the same mass.
Andreas Stohl of the University of Vienna said: “This could have implications for cloud processes and even for stratospheric ozone since it seems possible that microplastic fibres are abundant in the upper troposphere and might even reach the stratosphere.
“For instance, we cannot rule out chlorine in these particles harms the ozone layer. However, right now, we do not even know how much plastic, and in which sizes and shapes, is emitted into the atmosphere, and we also do not know what happens to it under the extreme conditions of the upper troposphere and stratosphere.”
He concluded: “We are lacking fundamental data. But we must be watchful given the dramatic increase in global plastic production.”
Despite all uncertainties, one thing is evident from the paper: the often peculiar shapes of microplastic fibres must be considered when investigating their environmental impact.
