SEASONAL VARIATION AND THEIR CHARACTERIZATION OF SUSPENDED PARTICULATE MATTER IN THE AIR OF SUBWAY STATIONS

Abstract In order to accumulate fundamental data on the atmospheric environments in subway, the mass concentration, particle size distribution and elemental constitution of suspended particulate matter (SPM), and the concentration and constitution of polycyclic aromatic hydrocarbon (PAH), were measured and analyzed at three subway stations with different air supply systems on the same line. The mass concentration of SPM in the subway stations showed seasonal variations, and was higher in December and October than in March and June. It was also higher at the subway stations than in the aboveground throughout the seasons. The concentrations of SPM in the size range of 0.5–5.0 μm were higher in the subway stations than aboveground, suggesting this size of SPM was generated by the operation of trains. The elements that were observed at high concentrations in the subway SPM were Fe, Ba, Cu and Ca. On the other hand, the elements of which concentrations were relatively higher in the aboveground air were Cl, Na and K. Polycylic aromatic hydrocarbons collected at the subway stations showed similar concentrations and characteristics to those observed in the urban atmosphere. Keywords: Subway stationSuspended particulate matterElemental constitutionPolycyclic aromatic hydrocarbon ACKNOWLEDGEMENTS The authors express their gratitude to the Teito Rapid Transit Authorities, Tokyo, Japan for granting permission for sampling and analysis of samples. The authors also thank Prof. Izumi Nakai and Dr. Yasuko Terada of Science University of Tokyo for their kind assistance of XRD analysis. This work was supported by a Grant-in-Aid for Science Research on Priority Areas from Ministry of Education, Science and Culture of Japan (#5278113, 1996).