Modelling the effect of shape on atmospheric microplastic transport

Microplastics are particles less than 5 mm in size and are a growing scientific concern, given the potential harm caused across ecosystems as a result of the global use of plastics. Most microplastics are non-spherical in shape, however, most atmospheric modelling studies to date treat microplastics as simple spheres when assessing transport. To further understand the effects of shape and size on atmospheric microplastic transport, the HYSPLIT model was utilized to identify potential differences. It was shown that the extent of microplastic transport and deposition varied significantly by shape for particles larger than 6 μm, but for particles smaller than 6 μm, the differences were not significant. Long fibres deposited over a 32% greater area than spherical particles at the largest equivalent size of 23.5 μm. The maximum deposition area occurred for particles with an equivalent size of 4.5 μm, varying in deposition area by less than 0.25% by the shapes considered. As particles smaller than 10 μm have a large potential to cause adverse health effects and shape affects transport in the 6 μm–10 μm size range, accurately modelling the shape of atmospheric microplastic transport is crucial to determining the range and amount of deposition globally.