Long-term observation of PM2.5 and water-soluble inorganic ions at central Tokyo, Japan

Abstract

Long-term exposure to fine particulate matter, PM2.5 has been inviting considerable attentions in relation to adverse health effects. In this study, PM2.5 samples were collected at Shibuya, Tokyo, Japan from July 2013 to Nov 2019 and atmospheric concentrations were determined for PM2.5 and its water-soluble inorganic ions. This paper aimed to characterize seasonal and yearly variations of atmospheric concentrations of PM2.5 and water-soluble inorganic ions using the seven-year result. The analytical results showed the concentration of PM2.5 ranged from 2.4 to 39 μg/m3 , with an arithmetic mean of 12 plus or minus 5.9 μg/m3 (n = 132) and higher in spring and winter. No apparent increasing or decreasing tendency was found for the annual variation of PM2.5 level. The variation of PM2.5 was mostly determined by the content of ammonium sulfate because of significant correlation with concentrations of NH4(+) and SO4(2-). However, slight decreasing tendency was found in SO4(2-) concentration for 7 years. Meanwhile, Na(+) concentration showed significant increase with time. These findings suggest potential changes in the quality of PM2.5 at the sampling site.