Component-specific information is crucial for identifying sources of PM2.5 in indoor environments. However, profiles of PM2.5 at various locations, including subway tunnels are limited. This study aimed to evaluate the relationships between PM2.5 and its component across tunnels, platforms, and outdoor environments at underground subway stations in Incheon. The study was conducted at six underground subway stations in Incheon. PM2.5 concentrations were measured twice at each station, simultaneously covering the tunnel, platform, and outdoor areas. Carbon (two types), ion (eight types), and metal components (20 types) were analyzed using each analytical instruments. The mean PM2.5 concentration in the tunnel was 33.0±15.7 μg/ m3, significantly higher than the concentrations observed on the platform (12.9±4.6 μg/m3) and outdoors (13.1±7.6 μg/m3). The proportion of total metal concentrations in PM2.5 was highest in the tunnel (57.8%), followed by the platform (22.2%) and outdoor areas (11.3%). Significant correlations between the platform and tunnel were observed for organic carbon, SO4 2–, NO3 –, NH4 +, Ba, Mn, Fe, and Se. Significant correlations between the platform and outdoor were observed for SO4 2–, NO3 –, NH4 +, and Ti, while the tunnel and outdoor showed correlations for SO4 2– and NH4 +. PM2.5 concentrations and total metal concentrations were highest in the tunnel. While PM2.5 concentrations on the platform and outdoors were similar, total metal concentrations were higher on the platform than outdoors. From the platform’s perspective, the concentrations of Ba, Mn, Fe, and Se were only associated with the tunnel, while SO4 2–, NO3 –, and NH4 + had tendency of correlations between both the tunnel and outdoors. The findings suggest that for platform PM2.5 concentrations, Ba, Mn, Fe, and Se may serve as indicators of tunnel-originating PM2.5, while SO4 2–, NO3 –, and NH4 + may serve as indicators for outdoor sources.

Abstract
1. 서 론
2. 연구 방법
    2.1 연구대상 및 기간
    2.2 중량 및 성분농도
    2.3 통계분석
3. 결 과
    3.1 PM2.5 농도
    3.2 성분 농도
4. 고 찰
5. 결 론
감사의 글
References

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• 원수란(이화여자대학교 환경공학과) | Soo Ran Won (Department of Environmental Science and Engineering, Ewha Womans Univwesity, Seoul)
• 황은설(국립환경과학원 환경기반연구부 생활환경연구과) | Eun Seol Hwang (Indoor Environment & Noise Research Division, National Institute of Environmental Research, Incheon)
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• 김홍경(국립환경과학원 환경기반연구부 생활환경연구과) | Hong-Kyoung Kim (Indoor Environment & Noise Research Division, National Institute of Environmental Research, Incheon)
• 이유진(인천교통공사) | Yujin Lee (Inchen Transit Corporation, Incheon)
• 이남호(인천교통공사) | Namho Lee (Inchen Transit Corporation, Incheon)
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