Efficient Atmospheric Transport of Microplastics over Asia and Adjacent Oceans

We developed a regional atmospheric transport model formicroplastics (MPs, 10 mu m to 5 mm in size) over Asia and the adjacent Pacificand Indian oceans, accounting for MPs'size- and shape-dependent aerodynamics.The model was driven by tuned atmospheric emissions of MPs from the land andthe ocean, and the simulations were evaluated against coastal (n= 19) and marine(n= 56) observations. Our tuned atmospheric emissions of MPs from Asia andthe adjacent oceans were 310 Gg y-1(1 Gg = 1 kton) and 60 Gg y-1, respectively.MP lines and fragments may be transported in the atmosphere >1000 km; MPpellets in our model mostly deposited near-source. We estimated that 1.4% of theMP mass emitted into the Asian atmosphere deposited into the oceans viaatmospheric transport; the rest deposited over land. The resulting netatmospheric transported MPflux from Asia into the oceans was 3.9 Gg y-1,twice as large as a previous estimate for the riverine-transported MPflux fromAsia into the oceans. The uncertainty of our simulated atmospheric MP budget was between factors of 3 and 7. Our workhighlighted the impacts of the size and morphology on the aerodynamics of MPs and the importance of atmospheric transport in thesource-to-sink relationship of global MP pollution