Microbeam analysis of yellow sand dust particles

A microbeam system was applied to analyses of yellow sand dust particles. Such particles from the Asian continent sometimes cause turbid conditions in Japan, especially in spring, and are sometimes changed by mixing with anthropogenic and marine aerosols. For better understanding of their formation mechanism, analysis of single particles is indispensable. For this purpose, we developed a microbeam analysis system at Tohoku University with a spatial resolution of better than 1 μm. The system comprises two x-ray Si(Li) detectors for particle-induced x-ray emission (PIXE), an annular ion-implanted Si detector for Rutherford backscattering (RBS), an ion-implanted Si detector for off-axis scanning transmission ion microscopy (STIM), and a Si-PIN photodiode for direct STIM analyses. The combination of PIXE, RBS and off-axis STIM methods enabled simultaneous analyses of hydrogen to metal elements and revealed the chemical compositions of these particles. Yellow sand dust particles were impacted on a thin polycarbonate film and analyzed using the microbeam analysis system. After quantification of the elemental components of these particles, the chemical composition of each particle was obtained. Silicon, calcium, oxygen, carbon, and hydrogen are the main composing elements of the particles originating mainly from soil dust from the Asian continent. The particles contain sulfur and heavier elements too, originating from mixing with anthropogenic aerosols. Sodium, magnesium, and chlorine, which come from marine aerosols, are also included in these particles and might be adsorbed during transport from the Asian continent. Single particle analysis of yellow sand dust will engender a better understanding of their formation process during transport.