Relative contributions of ambient air and internal sources to multiple air pollutants in public transportation modes

Zhiyuan Li; Wenwei Che; Md Shakhaoat Hossain; Jimmy C H Fung; Alexis K H Lau

doi:10.1016/j.envpol.2023.122642

Relative contributions of ambient air and internal sources to multiple air pollutants in public transportation modes

Environ Pollut. 2023 Dec 1:338:122642. doi: 10.1016/j.envpol.2023.122642. Epub 2023 Sep 30.

Authors

Zhiyuan Li¹, Wenwei Che², Md Shakhaoat Hossain³, Jimmy C H Fung⁴, Alexis K H Lau⁵

Affiliations

¹ School of Public Health (Shenzhen), Sun Yat-sen University, Guangzhou, 510275, China; Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China. Electronic address: zhiyuan.li@connect.ust.hk.
² Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; Hong Kong Environmental Protection Department, Revenue Tower, 5 Gloucester Road, Wan Chai, Hong Kong, China. Electronic address: joannawwche@epd.gov.hk.
³ Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; Department of Public Health and Informatics, Jahangirnagar University, Savar, Dhaka, 1342, Bangladesh. Electronic address: shakhaoat@juniv.edu.
⁴ Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; Department of Mathematics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China. Electronic address: majfung@ust.hk.
⁵ Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China. Electronic address: alau@ust.hk.

PMID: 37783415
DOI: 10.1016/j.envpol.2023.122642

Abstract

Commuters are often exposed to relatively high air pollutant concentrations in public transport microenvironments (TMEs) because of their proximity to emission sources. Previous studies have mainly focused on assessing the concentrations of air pollutants in TMEs, but few studies have distinguished between the contributions of ambient air and internal sources to the exposure of commuters to air pollutants. The main objective of this study was to quantify the contributions of ambient air and internal sources to the measured particulate matter and gaseous pollutant concentrations in selected TMEs in Hong Kong, a high-rise, high-density city in Asia. A sampling campaign was conducted to measure air pollutant concentrations in TMEs in Hong Kong in July and November 2018 using portable air quality monitors. We measured the concentrations of each pollutant in different TMEs and quantified the infiltration of particulate matter into these TMEs. The double-decker bus had the lowest particulate matter concentrations (mean PM₁, PM_2.5, and PM₁₀ concentrations of 5.1, 9.5, and 13 μg/m³, respectively), but higher concentrations of CO (0.9 ppm), NO (422 ppb), and NO₂ (100 ppb). For all the TMEs, about half of the PM_2.5 were PM₁ particles. The Mass Transit Railway (MTR) subway system had a PM_2.5/PM₁₀ ratio of about 0.90, whereas the PM_2.5/PM₁₀ ratio was about 0.60-0.70 for the other TMEs. The MTR had infiltration factor estimates <0.4 for particulate matter, lower than those of the double-decker bus and minibus. The MTR had the highest contribution from internal sources (mean PM₁, PM_2.5, and PM₁₀ concentrations of 4.6, 13.4, and 15.8 μg/m³, respectively). This study will help citizens to plan commuting routes to reduce their exposure to air pollution and help policy-makers to prioritize effective exposure reduction strategies.

Keywords: Air pollution exposure; Ambient air; Infiltration factor; Internal sources; Transportation modes.

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
Environmental Exposure
Hong Kong
Particulate Matter / analysis
Transportation

Substances

Air Pollutants
Particulate Matter