Experimental investigation of ultra-fine particle size distribution near a busy road

In this paper, evolution of the size distribution of fine and ultra-fine particles emitted from vehicles on a busy road is investigated experimentally. In particular, several different modes (distinct maxima) of the particle size distribution are investigated as a function of the distance from the road. An unusual and complex evolution of these modes is discovered. In particular, it is demonstrated that some of the modes tend to shift towards smaller particle size, which has never been reported previously. Complex correlation between the modes is determined experimentally. In addition, for the first time, the total number concentration is clearly shown to go through a significant maximum at some distance from the road. This could have significant influence on the assessment of exposure to fine and ultra-fine particles in the vicinity of busy roads.