The Size-Oriented Particulate Mass Ratios and Their Characteristics on the Seoul Metropolitan Subway Lines

Abstract

The purpose of the study was to initially investigate the concentration patterns of PM 1 , PM 2.5 and PM 10 in the Seoul subway lines, and then to figure out the PM behaviors of internal and external sources inside subway tunnels. The PMs were monitored by a light scattering real-time monitor during winter (Jan. 8-26 in 2015) and summer (July 2-Aug. 7 in 2015) in tunnel air, in passenger cabin air, and in the ambient air. The daily average PM 10 , PM 2.5 , and PM 1 concentrations on these object lines were 101.3±38.4, 81.5±30.2, and 59.7±19.9 μg/m 3 , respectively. On an average, the PM concentration was about 1.2 times higher in winter than in summer and about 1.5 times higher in underground tunnel sections than in ground sections. In this study, we also calculated extensively the average PM mass ratios for PM 2.5 /PM 10 , PM 1 /PM 10 , and PM 1 /PM 2.5 ; for example, the range of PM 2.5 /PM 10 ratio in tunnel air was 0.82-0.86 in underground tunnel air, while that was 0.48-0.68 in outdoor ground air. The ratio was much higher in tunnel air than in outdoor air and was always higher in summer than in winter in case of outdoor air. It seemed from the results that the in/out air quality as well as a proper amount of subway ventilation must be significant influence factors in terms of fine PM management and control for the tunnel air quality improvement.