Individual particle analysis in suburban Osaka

摘要

Higashi-Osaka city is urban area located on the east of Osaka city, Japan. The Higashi-Osaka campus of Kinki University is equipped with several ground-based instruments, including CIMEL sunphotometer supported by Aerosol Robotics Network (AERONET) and Suspended Particulate Matter (SPM) sampler. It is found from the in situ measurements that clear atmosphere with few small particles is not frequently observed; usually particles from diesel vehicles and industries are suspended in the atmosphere at the Higashi-Osaka campus. We analyzed atmospheric particles with scanning electron microscope coupled with energy dispersive X-ray analyzer under clear and dusty conditions. This instrument can detect contain elements of sample by X-ray emanated from the surface of the sample. In order to investigate change of particle properties before and after dust event, we select three cases defined as "before dust event", "peak of dust event", and "after dust event". The results of analyses indicate dominance of large nonspherical particles during the dust event. The main component of these particles is silicon from soil particles, which remain in the atmosphere after the dust event. The results of analyses for each case indicate that nonspherical particles with large particle size are dominant and the main component becomes silicon derived from soil particles at the peak of dust event and soil particles remain after dust event. Occasionally, anthropogenic pollutant can be transported to the Higashi-Osaka site before the dust event.