Large-Eddy Simulation of Non-Spherical Heavy Particle Transport in the Atmospheric Boundary Layer

Heavy particles in the atmosphere, such as microplastic particles and coarse dust particles, often exhibit non-spherical configurations. A key instance of this is microplastic particles, where recent studies increasingly highlight the importance of the atmosphere as a vital yet incompletely understood transport pathway. Microplastic fibers (MPFs), in particular, are estimated to represent a substantial proportion of airborne and deposited microplastics within both natural and built environments. This study explores the transport trajectories of MPFs in the atmospheric boundary layer (ABL) under varying atmospheric stability conditions, employing large-eddy simulation (LES) techniques. The gravitational settling speeds of MPFs are characterized using our newly developed model, which takes into account their unique morphology and the surrounding turbulent atmosphere. Simulation outcomes indicate notable variations in the spatial and temporal distributions of MPFs, depending on the specific properties of the fibers and the prevailing atmospheric stability conditions. These findings suggest the necessity of acknowledging the impact of non-spherical particle morphology in regional and global models, especially when dealing with heavy particles such as microplastics and coarse dust particles.