Combination of Bulk and Single Particle Analyses for Asian Dust

A multi-stage particle sampling instrument and a particle counter were operated at the ground monitoring site in Fukuoka where was directly exposed to the outflow of air masses from the Asian continent during the springtime of 2005. The bulk and individual dust particles were analyzed simultaneously by ICP-MS and micro-PIXE, respectively. The ground-based observation of dust storm by the Japan Meteorological Agency and by the NOAA HYSPLIT dispersion-trajectory model indicated that dust storm was driven from the Chinese continent including dust source area. The number concentration of gigantic particles (e.g., larger than 5 μm) was measured to be 10 times higher in an Asian dust storm (hereafter called “ADS”) period than in a non-ADS period. There is an outstanding increase of mass concentration in the range of 3.5-7.7 μm in ADS event. In ADS event, soil fraction accounts 57.9-70.1% of particle mass concentration in coarse particles larger than 3.5 μm. Micro-PIXE analysis enables us to classify individual dust particles into several types. The particles with 3.5-5.1, 5.1-7.7, and 7.7-10.9 μm experienced aging processes by 60.6, 69.2, and 77.2%, respectively. On the basis of the reconstructed elemental maps by micro-PIXE analysis, the chemical transformation of dust particles was also presumed.