Preprints
https://doi.org/10.5194/acp-2022-597
https://doi.org/10.5194/acp-2022-597
 
26 Sep 2022
26 Sep 2022
Status: this preprint is currently under review for the journal ACP.

Measurement Report: Abundance and fractional solubilities of aerosol metals in urban Hong Kong: Insights into factors that control aerosol metal dissolution in an urban site in South China

Junwei Yang1, Lan Ma1, Xiao He2, Wing Chi Au1, Yanhao Miao1, Wen-Xiong Wang1,3, and Theodora Nah1,3 Junwei Yang et al.
  • 1School of Energy and Environment, City University of Hong Kong, Hong Kong SAR, China
  • 2College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China
  • 3State Key Laboratory of Marine Pollution, City University of Hong Kong, Hong Kong SAR, China

Abstract. Water-soluble metals are known to produce greater adverse human health outcomes than their water-insoluble forms. Although the concentrations of water-soluble aerosol metals are usually limited by atmospheric processes that convert water-insoluble metals to water-soluble forms, factors that control the solubilities of aerosol metals in different environments remain poorly understood. In this study, we investigated the abundance and fractional solubilities of different metals in size-fractionated aerosols collected at an urban site in Hong Kong, and identified the factors that modulated metal solubilities in fine aerosols. The concentrations of total and water-soluble metals in fine and coarse aerosols were the highest during the winter and spring seasons due to the long-range transport of air masses by northly prevailing winds from emission sources located in continental areas north of Hong Kong. The study-averaged metal fractional solubilities spanned a wide range for both fine (8.8 % to 70.3 %) and coarse (1.4 % to 54.3 %) aerosols, but higher fractional solubilities were typically observed for fine aerosols. Sulfate was found to be strongly associated with both the concentrations of water-soluble Cr, Fe, Co, Cu, Pb, and Mn and their fractional solubilities in fine aerosols, which implied that sulfate-driven acid processing likely played an important role in the dissolution of the water-insoluble forms for these six metals. Further analyses revealed that these strong associations were due to sulfate providing both the acidic environment and liquid water reaction medium needed for the acid dissolution process. Thus, the variability in the concentrations of water-soluble Cr, Fe, Co, Cu, Pb, and Mn and their fractional solubilities were driven by both the aerosol acidity levels and liquid water concentrations, which in turn were controlled by sulfate. These results highlight the roles that sulfate plays in the acid dissolution of metals in fine aerosols in Hong Kong. Our findings will likely also apply to other urban areas in South China, where sulfate is the dominant acidic and hygroscopic component in fine aerosols.

Junwei Yang et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-597', Mingjin Tang, 11 Oct 2022
  • RC2: 'Comment on acp-2022-597', Anonymous Referee #2, 01 Nov 2022
  • RC3: 'Comment on acp-2022-597', Akinori Ito, 07 Nov 2022

Junwei Yang et al.

Data sets

Abundance and fractional solubilities of aerosol metals in urban Hong Kong: Insights into factors that control aerosol metal dissolution in an urban site in South China Yang, Junwei, Ma, Lan, He, Xiao, Au, Wing Chi, Miao, Yanhao, Wang, Wen-Xiong, & Nah, Theodora https://doi.org/10.5281/zenodo.7013770

Junwei Yang et al.

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Short summary
Water-soluble metals play key roles in human health and atmospheric processes. We report the seasonal abundance and fractional solubilities of different metals in aerosols collected in urban Hong Kong, South China, and the key factors that modulated solubilities of various metals in fine aerosols. Our results highlight the dual roles (i.e., acidifying the aerosol particle and providing a liquid reaction medium) that sulfate plays in the acid dissolution of metals in fine aerosols in Hong Kong.
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