Aerosol-CFD Coupled Model Simulations of Vehicle Exhaust and Non-Exhaust Particulate Matters Near Major Roadways

Near-road environment is highly exposed to vehicle exhaust and non-exhaust particles with a range of their sizes from a few nanometers to a few micrometers. Tail-pipe exhaust emissions of filterable and condensable particle matters are originated from the fossil fuel combustions, while non-exhaust emissions are attributed to sources of tyre wear, brake wear, and on-road resuspension. Atmospheric dispersion processes as well as aerosol dynamic processes (such as coagulation, condensation, etc.) have important roles in determining the distribution and transformation of emitted particles in near-road environments. This study aims to examine the distribution of exhaust and non-exhaust particles and their contributions to near-road air quality in roadside environments. To achieve this, we have developed a computational fluid dynamics (CFD) model coupled with an aerosol dynamics (PMDYN) module for simulating atmospheric dispersion and aerosol dynamics processes simultaneously. The study areas are major expressways in the Republic of Korea. The exhaust and non-exhaust emission factors with particle size distributions were obtained from laboratory and field experiments in terms of fuel and vehicle types. As a result of aerosol-CFD coupled model simulations, exhaust and non-exhaust and particles appeared to contribute greatly to the number and mass and concentrations, respectively. The major particle diameters of exhaust and non-exhaust particles were smaller than approximately 0.1 μm for number concentration and larger than approximately 1 μm for mass concentration, respectively. In addition to the particle size distribution, the contribution of on-road mobile sources highly dependent on emission types and roadside environments will be analyzed and presented.