DIURNAL PROFILE OF PARTICLE-BOUND POLYCYCLIC AROMATIC HYDROCARBON (PPAH) CONCENTRATION IN URBAN ENVIRONMENT IN TOKYO METROPOLITAN AREA

摘要

Traffic emits particles under 1 μm. The particles are the most responsible to particle-bound polycyclic aromatic hydrocarbon (pPAH) which can impact human health. To assess them as health hazards, we monitored diurnal changes in the concentration and distribution of pPAH near roads in Tokyo. The total pPAH concentration was determined using a photoelectric aerosol sensor (PAS) which ionized PAH-adsorbing particles. The total pPAH concentration was compared with chemical analyses by gas chromatography/mass spectrometry (GC/MS). Two sampling sessions, one in August and one in September 2000, were done at three sampling sites at the Hongo Campus of the University of Tokyo. Monitoring was every two minutes for six consecutive days for the first session and for seven consecutive days for the second session. Correlation of the pPAH concentration with traffic flow and with meteorological conditions were also assessed. The pPAH concentration varied in the same manner on all days: it sharply increased in the early morning by a sudden burden of traffic, and it rapidly decreased during the daytime, probably owing to photodegradation and/or dilution by rising in the mixing zone. The local wind field, and consequently the transportation of pPAH from the road, were strongly influenced by the configuration and location of the surrounding buildings. The pPAH clearly changed in 1- and 0.5 day cycles, particularly at the roadside.