Quantifying the impacts of PM2.5 constituents and relative humidity on visibility impairment in a suburban area of eastern Asia using long-term in-situ measurements

Yu-Chieh Ting; Li-Hao Young; Tang-Huang Lin; Si-Chee Tsay; Kuo-En Chang; Ta-Chih Hsiao

doi:10.1016/j.scitotenv.2021.151759

Quantifying the impacts of PM_2.5 constituents and relative humidity on visibility impairment in a suburban area of eastern Asia using long-term in-situ measurements

Sci Total Environ. 2022 Apr 20:818:151759. doi: 10.1016/j.scitotenv.2021.151759. Epub 2021 Nov 22.

Authors

Yu-Chieh Ting¹, Li-Hao Young², Tang-Huang Lin³, Si-Chee Tsay⁴, Kuo-En Chang⁵, Ta-Chih Hsiao⁶

Affiliations

¹ Graduate Institute of Environmental Engineering, National Taiwan University, Taipei, Taiwan.
² Department of Occupational Safety and Health, China Medical University, Taichung, Taiwan.
³ Center for Space and Remote Sensing Research, National Central University, Taoyuan, Taiwan.
⁴ NASA Goddard Space Flight Centre, Greenbelt, MD, USA.
⁵ Graduate Institute of Environmental Engineering, National Taiwan University, Taipei, Taiwan; Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan.
⁶ Graduate Institute of Environmental Engineering, National Taiwan University, Taipei, Taiwan; Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan. Electronic address: tchsiao@ntu.edu.tw.

PMID: 34822889
DOI: 10.1016/j.scitotenv.2021.151759

Abstract

The deterioration of visibility due to air pollutants and relative humidity has been a serious environmental problem in eastern Asia. In most previous studies, chemical compositions of atmospheric particles were provided using filter-based offline analyses, which were unable to provide long-term and in-situ measurements that resolve sufficient temporal variations of air pollution and meteorology, hindering the resolution of the relationship between air quality and visibility. Here, we present a year-long continuously measured data from a comprehensive suite of online instruments to investigate diurnal and seasonal impacts of the aerosol chemical compositions in PM_2.5 on visibility seasonally and diurnally. The measured dry aerosol extinction at λ = 550 nm reached a closure with that predicted by aerosol compositions within 12%. However, the hygroscopic growth of particles under ambient RH could enhance the aerosol extinction by a factor of 2-6, matching the perceptive visibility of the public. Particulate ammonium nitrate was most sensitive to reducing visibility, while ammonium sulfate contributed the most to the light extinction. In spring and winter, the monsoon and stagnant air masses reduced the visibility and increased PM_2.5 (>35 μg m^-3). The moisture was found to substantially enhance the light extinction under RH = 60-90%, reducing visibility by approximately 15 km, largely attributed to hygroscopic inorganic salts. This study serves as a metric to highlight the need to consider the influence of RH, and aqueous reactions in producing secondary inorganic aerosols on atmospheric visibility, underpinning the more accurate mitigation strategies of air pollution.

Keywords: Hygroscopic aerosols; In-situ measurements; Light extinction; Mitigation strategies; Relative humidity; Visibility.

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Air Pollution* / analysis
Asia, Eastern
China
Environmental Monitoring
Humidity
Particulate Matter / analysis
Seasons

Substances

Aerosols
Air Pollutants
Particulate Matter