Abstract
Individual particle analysis combined with cluster analysis of airborne particulates collected beside a roadway was performed to make a source apportionment and to conduct a methodological investigation. Samples (fractions Al-A8 and BF) were collected at a site situated at 0.5 m from the roadway by an Andersen air sampler. Fractions Al to A8 were collected on the 1st stage to 8th stage and the fraction BF was collected on the backfi lter of the sampler, respectively. Their aerodynamic sizes were >11μm, 7-11μm, 4.7-7μm, 3.3-4.7μm, 2.1 3.3μm, 1.1-2.1μm, 0.65-1.1μm, 0.43-0.65μm, and <0.43μm, respectively. Cluster analysis was performed on the EPMA results from individual particle analysis of 100 particles in each of Al-A8 fractions. The results of source apportionment for each fraction showed that the fractions of particle size >2.1μm had more tire dusts and soil minerals; and the fractions of particle size 0.43μm-2.1μm had more motor exhausted soot. Particles mainly containing iron, calcium, silicon or sea salt were also detected. Contributions of the seven kinds of cluster described above were 27, 10, 33, 9.5, 6.7, 4.0, and 1.7 by weight percent in total analyzed particles. Although particles of <0.43μm diameter were not analyzed, it is thought that the contribution of scot to total collected particles is far larger than 33%, because larger contribution of soot was observed in smaller particle fractions. So that, we can conclude that source apportionment of airborne particulates by this method is effective and practically useful.
