Deposition of Roadside Atmospheric Non-Tire Wear Microplastics: Characteristics and Influencing Factors

Atmospheric deposition of microplastics (MPs) contributes to the contamination of both terrestrial and aquatic environments. Roads show high MP deposition, yet the factors influencing the deposition rate and characteristics (polymer types and sizes) remain insufficiently understood. In this study, we investigated atmospheric MPs in two size fractions: 45–300 μm (small) and ≥300 μm (large), collected monthly for one year using a bulk deposition method. Large MPs were visually sorted and characterized via ATR-FTIR spectroscopy for polymer identification, while smaller MPs were quantified by measuring non-purgeable organic carbon (NPOC) using a total organic carbon (TOC analyzer), without polymer characterization. Deposition rates of large MPs ranged from 3 to 9 million pcs/ha/month, while small MPs averaged 72.2 gC/ha/month. Identified polymers included PP, PE, PS, PVC, PET, PVAC, PA, and PU. Traffic mainly influenced large MPs, especially PET and PA, near roads, whereas wind direction and intensity enhanced dispersal of small MPs and the transport of PVC, PS, and PU. Predominant easterly winds also indicated possible contributions from industrial and other anthropogenic sources. By focusing on the road area, integrating influence of traffic and meteorological factors, and adapting TOC-based carbon quantification, this study provides new insights and extends existing knowledge in the field.