Characteristics of Spatial Distributions of Ultrafine Particles and PM2.5 on the Roadways around Busan North Port: Effects of Traffic Composition and Local Meteorology

Abstract

Mobile measurements were conducted to understand the spatial distributions of the number concentrations of particles (PNC) with diameters from 20 to 700 nm and PM2.5 mass concentrations along two routes, Route GM and SD, the two characteristic roadways adjacent to Busan North Port with distinct traffic compositions. The measurements were conducted 11 times in the morning and 16 times in the afternoon of November 2021, October 2022, and January 2023, with about five repetitions each time. Despite the proximity of Route GM and SD (only about 340 m apart), the PNC in Route SD (9.7±4.4× 104 particles/cm3) was 2.6 times higher than those in Route GM (3.7±2.2×104 particles/cm3), whereas the differences in PM2.5 were not as significant as in PNC. These differences appear to be attributed to differences in traffic composition. While the total traffic volumes for both routes were similar throughout the day, the proportion of heavy-duty vehicles (HDV) differed significantly (SD route: 44%, GM route: 13%). Nonetheless, the PNC levels observed in both the roadways near Busan port were significantly high compared to those in urban areas worldwide. In addition, the mean size of particles in a higher PNC route was smaller than that in a lower PNC roadway, and the smaller size was linked to a larger deposition fraction in deeper respiration tracts of the human body. These findings suggest that the roadways trafficked with a large volume of HDV near the port could potentially risk public health, highlighting the need to monitor PNC and size distributions in those areas.