2009 Volume 44 Issue 1 Pages 24-32
We have carried out continuous measurements of PM2.5 semi-volatile compounds, which have been measured individually in the past time, in order to analyze seasonal factors affecting mass concentrations of them in a central Tokyo. PM2.5, nitrate, sulfate, EC and OC were also measured. Concentrations of PM2.5 volatile compounds during winter showed the highest of those during four seasons. Daily variation of the volatile concentrations was common to four seasons. There was an obvious peak at around noon and around 2:00 a.m. as well as nitrate, sulfate, OC and EC. After studying effects of composition, meteorological factors and traffic volume by multivariate analyses, it implies a single factor did not strongly influence on PM2.5 volatile compounds but multi-factors did comprehensively with multi-regression analyses. The most contributed variable was nitrate in all seasons. The next contributed variables were different according to the season, and it was revealed that they were absolute humidity during winter, temperature during autumn and summer, and time during spring and summer.