Sources and Characteristics of Particulate Matter in Subway Tunnels in Seoul, Korea

Yongil Lee, Young-Chul Lee, Taesung Kim, Jin Seok Choi and Duckshin Park
Additional contact information
Yongil Lee: Korea Railroad Research Institute (KRRI), 176 Cheoldobakmulkwan-ro, Uiwang-si 16105, Korea
Young-Chul Lee: Department of BioNano Technology, Gachon University, 1342 seongnamdae-ro, Seongnam-si 13120, Korea
Taesung Kim: Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Suwon-si 16419, Korea
Jin Seok Choi: Analysis Center for Research Advancement, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon-si 34141, Korea
Duckshin Park: Korea Railroad Research Institute (KRRI), 176 Cheoldobakmulkwan-ro, Uiwang-si 16105, Korea

IJERPH, 2018, vol. 15, issue 11, 1-17

Abstract: Hazards related to particulate matter (PM) in subway systems necessitate improvement of the air quality. As a first step toward establishing a management strategy, we assessed the physicochemical characteristics of PM in a subway system in Seoul, South Korea. The mean mass of PM 10 and PM 2.5 concentrations ( n = 13) were 213.7 ± 50.4 and 78.4 ± 8.8 µg/m 3 , with 86.0% and 85.9% of mass concentration. Chemical analysis using a thermal–optical elemental/organic carbon (EC–OC) analyzer, ion chromatography (IC), and inductively coupled plasma (ICP) spectroscopy indicated that the chemical components in the subway tunnel comprised 86.0% and 85.9% mass concentration of PM 10 and PM 2.5 . Fe was the most abundant element in subway tunnels, accounting for higher proportions of PM, and was detected in PM with diameters >94 nm. Fe was present mostly as iron oxides, which were emitted from the wheel–rail–brake and pantograph–catenary wire interfaces. Copper particles were 96–150 nm in diameter and were likely emitted via catenary wire arc discharges. Furthermore, X-ray diffraction analysis (XRD) showed that the PM in subway tunnels was composed of calcium carbonate (CaCO 3 ), quartz (SiO 2 ), and iron oxides (hematite ( α -Fe 2 O 3 ) and maghemite-C ( γ -Fe 2 O 3 )). Transmission electron microscopy images revealed that the PM in subway tunnels existed as agglomerates of iron oxide particle clusters a few nanometers in diameter, which were presumably generated at the aforementioned interfaces and subsequently attached onto other PM, enabling the growth of aggregates. Our results can help inform the management of PM sources from subway operation.

Keywords: characteristics; particulate matter; source identification; subway tunnel; air quality (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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