Optical properties, source apportionment and redox activity of humic-like substances (HULIS) in airborne fine particulates in Hong Kong

Yiqiu Ma; Yubo Cheng; Xinghua Qiu; Gang Cao; Binyu Kuang; Jian Zhen Yu; Di Hu

doi:10.1016/j.envpol.2019.113087

Optical properties, source apportionment and redox activity of humic-like substances (HULIS) in airborne fine particulates in Hong Kong

Environ Pollut. 2019 Dec;255(Pt 1):113087. doi: 10.1016/j.envpol.2019.113087. Epub 2019 Aug 24.

Authors

Yiqiu Ma¹, Yubo Cheng¹, Xinghua Qiu², Gang Cao³, Binyu Kuang⁴, Jian Zhen Yu⁴, Di Hu⁵

Affiliations

¹ State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Kowloon, Hong Kong SAR, PR China.
² State Key Joint Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Center for Environment and Health, Peking University, Beijing 100871, PR China.
³ School of Civil and Environment Engineering, Harbin Institute of Technology Shenzhen Graduate School, Shenzhen, 518057, PR China.
⁴ Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, PR China.
⁵ State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Kowloon, Hong Kong SAR, PR China; HKBU Institute of Research and Continuing Education, Shenzhen Virtual University Park, Shenzhen, 518057, PR China. Electronic address: dihu@hkbu.edu.hk.

PMID: 31541815
DOI: 10.1016/j.envpol.2019.113087

Abstract

Humic-like substances (HULIS) account for a considerable fraction of water-soluble organic matter (WSOM) in ambient fine particulates (PM_2.5) over the world. However, systemic studies regarding the chemical characteristics, sources and redox activity of HULIS are still limited. In this study, the mass concentration, optical properties, and reactive oxygen species (ROS)-generation potential of HULIS were investigated in PM_2.5 samples collected in Hong Kong during 2011-2012, and they all showed higher levels on days under regional pollution than on days under long range transport (LRT) pollution and local emissions. Positive matrix factorization (PMF) analysis was conducted regarding the mass concentration and dithiothreitol (DTT) activity of HULIS. Four primary sources (i.e. marine vessels, industrial exhaust, biomass burning, and vehicle emissions), and two secondary sources (i.e. secondary organic aerosol formation and secondary sulfate) were identified. Most sources showed higher contributions to both the mass concentration and DTT activity of HULIS on regional days than on LRT and local days, except that marine vessels had a higher contribution on local days than the other two synoptic conditions. Secondary processes were the major contributor to HULIS (54.9%) throughout the year, followed by biomass burning (27.4%) and industrial exhaust (14.7%). As for the DTT activity of HULIS, biomass burning (62.9%) and secondary processes (25.4%) were found to be the top two contributors. Intrinsic ROS-generation potential of HULIS was also investigated by normalizing the DTT activity by HULIS mass in each source. HULIS from biomass burning were the most DTT-active, followed by marine vessels; while HULIS formed through secondary processes were the least DTT-active. For the optical properties of HULIS, multiple linear regression model was adopted to evaluate the contributions of various sources to the light absorbing ability of HULIS. Biomass burning was found to be the only source significantly associated with the light absorbing property of HULIS.

Keywords: Hong Kong; Optical properties; Oxidative potential; PM(2.5)-bound HULIS; Source apportionment.

MeSH terms

Aerosols
Air Pollutants / analysis
Air Pollutants / chemistry*
Coal / analysis
Dust / analysis
Environmental Monitoring / methods*
Hong Kong
Humic Substances / analysis*
Oxidation-Reduction
Particulate Matter / analysis
Particulate Matter / chemistry*
Solubility
Vehicle Emissions / analysis*
Water / chemistry

Substances

Aerosols
Air Pollutants
Coal
Dust
Humic Substances
Particulate Matter
Vehicle Emissions
Water