In this study we investigated the air pollutants dispersion around depressed road using commercial FLUENT CFD code. In order to find optimal turbulence model which simulates air pollution dispersion around. depressed road, we used the realizable k-ε model, the RNG k-ε model, and the Shear-Stress Transport k-⍵turbulence model in FLUENT CFD code. The results were compared with the wind tunnel experiments. Realizable k-ε turbulence model provided the best prediction for the surface concentrations and concentration profiles of selected downwind positions of the depressed road. It was found that a noise barrier, which positioned around the depressed road, decrease the horizontal impact distance lower 0.46~0.81 times and change the vertical air pollution impact distance larger 0.95~1.47 times than those of no barrier case. It was also found that two or three noise barriers increase 1.33-1.42 times the vertical air pollution impact distance. It contributes the decrease of horizontal air pollution impact distance 0.44~0.60 times compare with no barrier case.

The dispersion of air pollution in complex situations such as the cases of the filled road is a significant problem for the public safety and living quality. Application of computational fluid dynamics (CFD) helps to build the model calculation in order to estimate the dispersion of air pollutants. In order to assess its accuracy, this study used the Realizable k-ε model, the RNG k-ε model, and the Shear-Stress Transport k-ω turbulence model in FLUENT CFD code. The results were compared with the wind tunnel experiments. The Realizable k-ε turbulence model provided the best prediction for the surface concentration and concentration profiles of selected downwind positions of the filled road. It was found that a noise barrier, which positioned on the filled road, increases the vertical air pollution impact distance larger 1.75~1.92 times and decrease the horizontal impact distance lower 0.46~0.54 times than those of no barrier case. It was also found that two or three noise barriers increase 1.63~1.79 times the vertical air pollution impact distance. It contributes the decrease of horizontal air pollution impact distance 0.49~0.63 times compare with no barrier case.

Noise barriers along the road do not only block the traffic noise but also prevent traversing the car exhausts. These barriers may affect air pollution dispersion, leading to increase vertical mixing due to the upwind deflection of air flow caused by the noise barriers. In this study we investigated the air pollution dispersion around multi-noise barriers using commercial software FLUENT. Investigated cases were 8 cases which had from zero to three noise barriers and two emission sources. Simulated results show noise barriers increase the vertical air pollution impact distance larger 1.7~2.1 times than that of no barrier case. It was also found that noise barriers decrease the horizontal air pollution impact distance lower 0.6~0.8 times than that of no barrier case.

To investigate the effect of single windbreak and combination of hill and windbreak on pollutant dispersion in neutral boundary condition, CFD (Computational Fluid Dynamics) modeling was used. The validity of the CFD model was confirmed by wind tunnel and field experiments of single closed windbreak. The results show increased windbreak height increasing the height of maximum concentration position and decreasing surface concentration (x=50 m) from 1.5 to 5.0 times smaller than that of non-windbreak case. In combination of hill and windbreak case increasing hill height decreasing surface concentration from 1.0 to 1.1 times smaller than that of single windbreak case.

Because many recent epidemiological studies have reported the associations of population’s proximity to high traffic roadways with adverse health effects, interest in how roadside structures affect the concentration of motor vehicle emitted pollutants in the near-road microenvironment has increased. These noise barriers may affect pollutant (for example: odor, carbon dioxide, particle et al.) concentrations around structure by blocking initial dispersion. This study examined the effects of roadside barriers on the flow patterns and dispersion of pollutants from high traffic highway. The effects of noise barriers were examined using commercial software FLUENT. The results show noise barriers increase concentration of near noise barrier wake region and decrease concentration in the faraway distance from noise barrier. The results also show far from emission position (between 100 m and 200 m) surface concentration of multi-barrier cases are 2 times lower than that of no barrier case.

Currently, portable equipment for recycling of waste asphalt concrete (ASCON) has been used. However, any air pollution control devices are not attached in the simple portable one. Thus, a lot of air pollutants have been produced from recycling processes of waste ASCON which resulted from aging of paved roads or repavement of roads. This study deals with a preliminary result of concentration analysis of air pollutants obtained from a pilot and a real recycling processes of waste ASCON using simple portable recycling equipment. Air pollutants were taken from 4 steps of the pilot recycling process including an initial heating by liquid petroleum gas (LPG), intermediate heating and melting (H&M) process, final H&M process, and pavement processes using recycled ASCON at the recycling site. Also, air pollutants were taken front 4 steps of the real recycling processes including an initial H&M, final H&M and mixing, loading of recycled ASCON to dump trucks, and at the recycling site after leaving the loaded dump trucks for real pavement sites. The air pollutants measured in this study include volatile organic compounds (VOCs), aldehydes, particulate matter (PM: PM1, PM2.5, PM7, PM10, TSP (total suspended particulate)). The identified concentrations of VOCs increased with increasing time or degree for H&M of waste ASCON. In particular, very high concentrations of the VOCs at the status of complete melting, which is exposed to the air, of the waste ASCON just before paving tv the recycled ASCON at the recycling site. Also, considerable amount of VOCs were identified from the recycling equipment after the dump trucks leaded by recycled ASCON leaved the recycling site for the pavement sites. The relative level of formaldehyde exceeded 80% of the aldehydes Identified in the recycling processes. This is because the waste ASCON is exposed to direct flame of LPG during H&M processes. The PM concentrations measured in the winter recycling processes, such as the loading and rotation processes of waste ASCON into/in the recycling equipment for H&M, were much higher than those in the summer ones. In particular, the concentrations of coarse particles such as PM7 and PM10 during the winter recycling were very high as compared those during the summer one.