Characterization of Suspended Particulate Matter in the Air in Subways and Corresponding Above-ground Areas.

  • OKINAGA Kiyo
    Department of Applied Chemistry, Faculty of Sience, Science University of Tokyo
  • TAKAHASHI Sentaro
    The 4th Research Group, National Institute of Radiological Sciences
  • TSUGOSHI Takahisa
    The 4th Research Group, National Institute of Radiological Sciences
  • KUDO Yoshiyuki
    Department of Applied Chemistry, Faculty of Sience, Science University of Tokyo
  • FURUYA Keiichi
    Application Laboratory, Rigaku Industrial Co. Ltd.
  • ARAKI Yoichi
    Application Laboratory, Rigaku Industrial Co. Ltd.

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  • 地下鉄およびその近傍の地上部における大気中浮遊粒子状物質の特性

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Abstract

Size distribution, concentration, and chemical composition of suspended particulate matter (SPM) in subway cabins and stations on the Ginza Line in Tokyo were investigated on Saturdays in May, July and August, 1996. At all the subway stations, mass concentrations of SPM estimated with a dust counter were consistently below the level recommended by the Law for Maintenance of Sanitation in Buildings, Japan (<0.15mg/m3). There were marked variations in SPM mass concentrations among the subway stations, and the patterns of the variations were essentially the same on three different measuring days. In contrast, SPM mass concentrations at the corresponding above-ground areas did not vary so markedly, suggesting that the air supply systems at each station may play an important role in maintaining air quality. The relative concentrations of SPM with 0.3 0.5μm diameter were lower at all stations than at the corresponding above-ground areas, especially at the stations with reltaively higher mass concentrations of SPM. On the other hand, the relative concentrations of SPM with 0.5-3.0μm diameter appeared to be higher in the air at the subway stations than at the corresponding above-ground locations. Since similar findings have been observed in large underground shopping areas, this distinctive size distribution may be a common feature of underground SPM. Scanning electron microscopy showed that SPM collected in subways contained a relatively large number of aggregated metal fume-like particles, and that their iron concentration was significantly higher than that of SPM collected above-ground.

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