Electrification of wind-blown microplastics and its implication for transport of floating microplastics in air.

An ongoing debate exists on the magnitude of microplastics (MPs) emissions from the soil-air interface. Electrification of airborne microplastics MPs complicated the issue of modelling the transport of MPs by wind. Here, we first report new observations of wind-blown MP particles pronounced charged through wind tunnel experiments. The charges of individual MP particles are from -1.05-6.89 pC. The results suggest that relative humidity and particle size dictated the charges and polarity of MPs. An unsaturated charge model for individual MPs is derived. It simulated that the electrification of wind-blown MP pellet, fragment, and fiber significantly influences their dry settling velocity. The negatively (positively) charging MPs can migrate longer-distance during sand storms with upward (downward) electric fields. Irrespective of the electrification of MPs, it can lead to significant uncertainties in simulating the atmospheric MPs transport. This study thus highlights an important, previously unexplored, role of the electrification of MPs on the transport of floating MPs in air, and provides a new perspective on how charged MPs are influenced by atmospheric electric fields, thereby facilitating the understanding of the detailed motion trajectory and regional transport of MPs.