Characterization of PM 2.5, PM 2.5–10 and PM > 10 in ambient air, Yokohama, Japan

Abstract

This study elucidated the characteristics of ambient PM 2.5, PM 2.5–10 and PM > 10 with water soluble ions, i.e., Cl −, NO 3 −, SO 4 2−, Na +, NH 4 +, K +, Mg 2+ and Ca 2+ 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 PM 2.5, PM 2.5–10 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 PM 2.5, PM 2.5–10 and PM > 10 were 20.6, 9.6 and 5.1 µg m − 3 , respectively. The results of the daily PM 2.5 concentrations indicated that 67% of the daily PM 2.5 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 PM 2.5, PM 2.5–10 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 PM 2.5 are anthropogenic. On the other hand, a large proportion of sea salt particles contributes to PM 2.5–10 and PM > 10 . Spearman correlation indicated that the concentrations of OC and EC in PM 2.5 can originate from similar type of sources. However, the concentration of OC and EC in PM 2.5–10 and PM > 10 can have multiple sources. In addition, some atmospheric reactions were also characterized in this study.