Source Apportionment of Individual Airborne Particle in Underground Center by Using Electron Probe Microanalyzer

Abstract

The airborne suspended particulate matter (SPM) in urban artificial space consists of many kinds of particles emitted from different sources. The air in these spaces seems to be polluted by SPM particles emitted from sources in these spaces and apart from these spaces. Specifying the emission source of SPM particle is an important subject for environmental hygiene. The composition of each SPM particle is directly related to its origin. The conventional source apportionment methods are based on the bulk chemical analysis. Bulk chemical analysis, however, cannot offer direct information about sources, because only an average composition of collected SPM particles is obtained from such analysis. In this study, we developed a novel approach to the source apportionment of SPM particles by the combination of the sampling by the personal air sampler, the measurement of SPM weight concentration by the Piezo-balance mass monitor, the individual analysis by electron probe microanalyzer and a kind of multivaliant cluster analysis, median cluster analysis, using composition of each particle. This method was applied to SPM particles collected at underground center, underground parking and the traffic route near the ventilation in these artificial spaces in Kyushu area. Three SPM samples were collected at different time on a day: morning, daytime and night. From the results, it was clear that ( i ) the air in these artificial spaces were polluted from the SPM particles emitted from these spaces and pollutants in outside atmosphere, ( ii ) the ventilating system in these artificial spaces had a large effect on the composition of SPM particles in the air in these spaces, (iii) the structure of artificial space and design of ventilating system are very important factors for the control of air pollution in artificial spaces. We concluded that the developed method is powerful for the source apportionment of airborne SPM particles of polluted urban atmosphere.