Characterization of PM2.5, PM2.5–10 and PM> 10 in ambient air, Yokohama, Japan

This study elucidated the characteristics of ambient PM2.5, PM2.5–10 and PM> 10 with water soluble ions, i.e., Cl−, NO3−, SO42−, Na+, NH4+, K+, Mg2+ and Ca2+ and carbonaceous aerosol, i.e., EC and OC in above size fractions from the samples collected for the period of 2007–2008. The total numbers of PM2.5, PM2.5–10 and PM> 10 samples collected with MCI sampler were 91, 87 and 79, respectively. The ambient particulate samples were collected twice in a week for a period of 24 h at the roof of a three-storied building in Yokohama National University. The annual arithmetic mean concentrations of PM2.5, PM2.5–10 and PM> 10 were 20.6, 9.6 and 5.1 µg m− 3, respectively. The results of the daily PM2.5 concentrations indicated that 67% of the daily PM2.5 exceeded USEPA National Ambient Air Quality Standards (NAAQS) (15 µg m− 3) while 95% in respect of WHO ambient air quality guidelines (10 µg m− 3). The concentrations of water soluble ions in PM2.5, PM2.5–10 and PM> 10 accounted for 40%, 31% and 19%, respectively. The estimation of non-sea-salt particles implies that the major sources of water soluble ions in PM2.5 are anthropogenic. On the other hand, a large proportion of sea salt particles contributes to PM2.5–10 and PM> 10. Spearman correlation indicated that the concentrations of OC and EC in PM2.5 can originate from similar type of sources. However, the concentration of OC and EC in PM2.5–10 and PM> 10 can have multiple sources. In addition, some atmospheric reactions were also characterized in this study.