Effects of wind speed and atmospheric stability on the air pollution reduction rate induced by noise barriers

People around the world increasingly live in urban areas where traffic-related emissions can reach high levels, especially near heavy-traffic roads. It is therefore necessary to find short-term measures to limit the exposure of this population and noise barriers have shown great potential for achieving this. Nevertheless, further work is needed to better understand how they can act on pollution reduction. To do this, a Reynolds-Averaged Navier-Stokes model that takes into account thermal effects is used to study the effects of wind speed and atmospheric stability on the concentration reduction rates (CRR) induced by noise barriers. This study shows that the CRR behind the barriers may depend on both wind and thermal conditions. Although only the wind direction, and not the wind speed, has an impact on CRR in a neutral atmosphere, this parameter can be changed by both wind speed and thermal variations in non-neutral atmospheres. Stable cases lead to a higher CRR compared to unstable cases, while the neutral case gives intermediate results. Finally, it is shown that the variation of CRR is negligible for Richardson numbers ranging from similar to 0.50 to 0.17.