One-week samples of atmospheric aerosols were divided into five portions and were collected every two months. The high concentration of suspended particulate matter (SPM) was discussed in connection with seasonal changes in the measured component elements and the weather conditions. In order to investigate the influence of weather factors on the SPM high concentration phenomena, we tried four-hour measurements of gaseous and particulate nitrate, chloride and ammonium. The following points have been revealed.

(1) The component ratios of Cl^- and NO₃^-, the main constituents of secondary formed aerosols, to PM1.1 were remarkably increased in Nov. and Feb.

(2) The mass concentrations of SPM were extremely high with increasing relative humidity in the rainy season in the Kanto area. At the same time, the concentrations of not only SO₄^2- but also NO₃^-, which has been generally suggested to be in low concentration in the summer, were exceedingly high.

(3) The partition ratio of nitrate, gaseous nitrate / (gaseous nitrate + particulate nitrate), increased with an increase in the atmospheric temperature, and with a decrease in the relative humidity.

(4) The inorganic volatile matter (nitrate, chloride, ammonium) can be converted into particles by the influence of the temperature and humidity, and cause a high SPM concentration. The gas-to-particle conversion of the inorganic volatile matter was connected with the concentration of sulfate and sodium in the aerosol.