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Time-Dependent Size-Resolved Bacterial and Fungal Aerosols in Beijing Subway
Hanqing Fan1, Xinyue Li1,2, Jiahao Deng1, Guillaume Da3, Evelyne Gehin3, Maosheng Yao1
1 State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
2 School of Water Resources and Environment, China University of Geosciences, Beijing 100083, China
3 CERTES, Université Paris-Est Créteil, Laboratoire de Physique des Aérosols, 61 avenue du Général de Gaulle, 94000, Créteil, France
- Subway riders strongly influence weekday microbial aerosol during peak hours.
- Three times higher bioaerosol levels at 0.8–3 µm were observed for peak hours.
- Subway ventilation influences the subway bioaerosol size distribution levels.
- Different microbial aerosol species were observed among the subway stations.
Despite of an important concern, human bioaerosol emission into subway is not well and directly characterized. Here, we used bioaerosol detector and next generation sequencing methods to investigate time-dependent bioaerosol size distributions in Beijing subway system between March and April, 2015. In contrast to weekends, weekday microbial aerosol results exhibited strong time dependence with higher bacterial and fungal aerosol levels up to 2083 CFU m–3 and 483 CFU m–3 observed, respectively, for the peak hours. During the peak hour (17:30–18:30), bioaerosol emissions at 0.8–3 µm was detected, while about three times higher concentration levels were observed compared to those during the off-peak hour (22:00–23:00). Similar bioaerosol size distributions were observed between ventilation outlets and subway platform air. During off-peak hours, subway bioaerosols had similar size distributions with the outside air. Sequence results revealed a vast array of airborne microbial species which varied from one station to another, but with Aspergillus spp. as dominant fungal species, and Staphylococcus, Pseudomonas as primary bacterial genera including human opportunistic ones. Our results provide direct online observations of human contributions to subway size-resolved bioaerosols, and enhancing ventilation system might help for controlling the exposure especially during the peak-hours.
Bacteria; Fungi; Beijing subway; Fluorescent bioaerosol particle; Ventilation.