Global microplastic emission and deposition fluxes at the ocean-atmosphere interface

While microplastics (MP) have been recently identified and recognized as a pollutant for the atmospheric environment, little is known about their actual emissions and concentration in the atmosphere. In this work, we follow a bottom-up approach to estimate the fluxes of MP at the ocean-atmosphere interface.Coupling a sea spray emission scheme (Grythe et al. 2014) with the MP concentrations over the ocean surface simulated by the NEMO-PISCES general circulation model (Nucleus for European Modelling of the Ocean, Pelagic Interaction Scheme for Carbon and Ecosystem Studies, Richon et al. 2022), we estimate the global sea spray MP emissions at 6-hourly resolution, over a one-year period.The MP emission fluxes are then fed into the Lagrangian atmospheric dispersion model FLEXPART (Stohl et al., 2005; Pisso et al., 2019), driven with hourly ERA5 data at 0.5° horizontal resolution, to provide a global picture of the atmospheric cycle of the MP of marine origin.We discuss the main emission areas and their marked seasonal variability, the resulting atmospheric concentration across the globe and the deposition fluxes on both land and ocean surfaces. Finally, we compare simulated fluxes and concentrations with existing observations of MP in the marine atmosphere.