Reduction of atmospheric fine particle level by restricting the idling vehicles around a sensitive area.

The emission of idling vehicles strongly affects the levels of particles and relative pollutants in near-ground air around a school area. The PM2.5 mass concentration at a campus site increased from the background site by 15%, whereas NO3- and anthropogenic metals also significantly increased. Meanwhile, the PM2.5 contribution from mobile source in the campus increased 6.6% from the upwind site. An idling prohibition took place and showed impressive results. Reductions of PM2.5, ionic component, and non-natural metal contents were found after the idling prohibition. The mobile monitoring also pointed out a significant improvement with the spatial analysis of PM2.5, PM0.1, PAH, and black carbon concentrations. These findings are very useful to effectively improve the local air quality of a densely city during the rush hour.