Comparison of Ultrafine and Nanoparticles in Different Public Transportation Stations

Abstract

MM4-PD-12 Introduction: This study is designed to compare number concentrations of ultrafine and nanoparticles in public transportation stations. Method: The number concentrations and size distribution of PM with size range of 9.8 to 874.5 nm were measured by a scanning mobility particle sizer (SMPS) in 4 bus stations, 3 train stations, and 4 mass rapid (MRT) stations in Taipei from January 17, 2005 to March 18, 2005. Among them, there were 2 underground train stations and 3 underground MRT stations. The sampling duration is about 17.5 hours in each station. The particle data were classified to ultrafine particles (number concentration with size between 10 nm and 100 nm, NC0.01–0.1) and nano particles (number concentrations with size between 10 nm and 50 nm, NC0.01–0.05). One-way ANOVA and Scheffé test was used to compare the difference between 3 types of stations and difference between ultratfine and nanoparticles. NC0.01–0.1 exposures of public transportation users were also estimated by combining NC0.01–0.1 concentrations in stations and commuters’ waiting time, and ventilation rate together. Result: Hourly average number concentrations of NC0.01–0.1 in bus, train, and MRT stations were 12.8 × 104 cm−3, 6.4 × 104 cm−3 and 3.6 × 104 cm−3, respectively. As for NC0.01–0.05, hourly average number concentrations were 11.0 × 104 cm−3, 3.9 × 104 cm−3 and 2.6 × 104 cm−3. The percentage of number concentrations of accounted NC0.01–0.05 was about 78.5% in bus stations, but 46.6% and 47.1%, respectively, in underground MRT stations and train stations. For train and MRT stations, the number concentrations of NC0.01–0.1 at indoors were higher than those outdoors. Moreover, the number concentrations at MRT and bus stations in rush hours were higher than those in non-rush hours. We found the same results for NC0.01–0.05. Adult commuters’ annual NC0.01–0.1 exposures were 1.77 × 1013 particles in bus stations, 5.76 × 1012 particles in train stations, and 2.84 × 1012 particles in MRT stations. Discussion and Conclusions: The NC0.01–0.1 concentrations in public transportation stations varied by the distance between the stations and on-road vehicle emission sources in Taipei. The vehicle emission does contribute to the increase of NC0.01–0.05 particles. The NC0.01–0.1 concentrations in bus stations were significantly higher than those in train and MRT stations. Accordingly, bus users’ annual NC0.01–0.1 exposures were 1.19 × 1013 counts higher than train users, and 1.48 × 1013 counts higher than MRT users.