Interannual Variability in PM_2.5 Mass and Inorganic Ionic Components Measured in Komae, Tokyo

Abstract

Concentrations of PM_2.5 mass and inorganic ionic components measured in Komae, Tokyo, from FY1998 to FY2005 are analyzed for studying the interannual variability. It is found that the mass concentration tends to decrease annually, and this tendency is pronounced in winter. It is considered from the comparisons with other studies in South Kanto that the decreasing tendency is a relatively large-scale phenomenon, and the PM_2.5 mass concentration is being uniformed in the area.
Inorganic ionic species do not show such decreasing tendency in general. As a result, concentration ratios of secondary inorganic aerosol (SIA) to PM_2.5 mass tend to increase. This could lead to the uniformity in PM_2.5 mass concentration. The SIA concentration is high, very close to the US Air Quality Standard for PM_2.5. Therefore, the SIA should be more concerned in order to reduce the PM_2.5 mass concentration.