During the last decade,the importance of global warming has been recognized worldwide. Atmospheric aerosols
play an important role in the global warming/cooling effects. The physicochemical properties of aerosol particles are
fundamental to understanding such effects. In this study,the PIXE technique was applied to measure the average
chemical properties of aerosols. Micro-PIXE was also applied to investigate the mixing state of the individual aerosol
particle. The chemical composition data were used to estimate the optical properties of aerosols. The average values of
aerosol radiative forcing were 1.53 w/m2 in Kyoto and þ3.3 w/m2 in Nagoya,indicating cooling and warming effects
respectively. The difference of radiative forcing in the two cities may be caused by the large difference in chemical
composition of aerosols.