Characterization of Particles in Road Surface Sediments for Analyzing Runoff Behavior of Microplastics

Abstract

The particle behavior during stormwater runoff depends on particle characteristics, such as size and density, and for analyzing the behavior of particles, including microplastics, it is necessary to obtain basic data on the characteristics of various particles in environmental samples. In this study, we obtained number-based particle characterization data for all particles in road dust and sediment in a stormwater inlet by estimating particle density using solutions of different densities, calculating shape property values by image analysis, and identifying the material composition by ATR-FTIR. More than 90% of the particles in all samples were distributed in the density fraction higher than 1.6 g cm^-3. For morphological characteristics, the sediment in the stormwater inlet contained more small particles than road dust, and there might also be many aggregated particles, where fine particles had adhered to each other. About 40-50% of the particles were identified as synthetic polymer, and many synthetic polymer particles were distributed in the density fraction higher than 1.6 g cm^-3 and the Feret diameter fraction of 500-800 μm.