Major factors affecting the aerosol particulate concentration in the underground stations

Abstract

Based on the estimation of mass balance with measurement at several places in the underground stations, such as concourse, platform and tunnel, it was found that a major fraction of PM10 was metallic particles which were generated by the friction between train wheel and rail, brake disk and shoe, and pantograph and catenary in the tunnel. According to an analysis on the variation pattern, the spread direction, and the transport time of PM10, and on the elemental composition of PM10 at various places in underground stations, the particles generated and accumulated in the tunnel appear to be scattered and transported to the platform and other areas of concourse by the train-induced wind. To verify this hypothesis, the maximum speed of operating trains approaching to Nonhyeon Station in the Seoul Subway Line 7 was reduced from 75 km·h−1 to 45 km·h−1 except during the rush hours. When reducing the train speed, the ratios of Nonyeon Station and outdoor PM10 mass concentration were reduced by 43%, 40% and 48% at the tunnel, the concourse and the platform, respectively. Therefore, the particles-causing factors in the underground station were identified as the train-induced wind.