Hydroxyl Dicarboxylic Acids at a Mountainous Site in Hong Kong: Formation Mechanisms and Implications for Particle Growth.

Journal: ACS environmental Au
Published Date: Mar 14, 2025

Abstract

Secondary organic aerosol (SOA) has been shown to significantly impact climate, air quality, and human health. Hydroxyl dicarboxylic acids (OHDCA) are generally of secondary origin and ubiquitous in the atmosphere, with high concentrations in South China. This study explored the formation of representative OHDCA species based on time-resolved measurements and explainable machine learning. Malic acid, the most commonly studied OHDCA, had higher concentrations in the noncontinental air (63.7 ± 33.3 ng m) than in the continental air (7.5 ± 1.4 ng m). Machine learning quantitatively revealed the high relative importance of aromatics and monoterpenes SOA, as well as aqueous processes, in the noncontinental air, due to either shared precursors or similar formation pathways. Isoprene SOA, particle surface area, and ozone corrected for titration loss (O ) also elevated the concentrations of malic acid in the continental air. Aqueous photochemical formation of malic acid was confirmed given the synergy between LWC, temperature, and O . Moreover, the OHDCA-like SOA might have facilitated a relatively rare particle growth from early afternoon to midnight in the case with the highest malic acid concentrations. This study enhances our understanding of the formation of OHDCA and its climate impacts.

Authors

  • Hongyong Li
    Environment Research Institute, Shandong University, Qingdao 266237, China.
  • Xiaopu Lyu
    Department of Geography, Faculty of Arts and Social Sciences, Hong Kong Baptist University, Hong Kong 999077, China.
  • Likun Xue
    Environment Research Institute, Shandong University, Qingdao 266237, China.
  • Yunxi Huo
    Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University,Hong Kong 999077, China.
  • Tianshu Chen
    Clinical Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, P. R. China.
  • Dawen Yao
    School of Intelligent Systems Engineering, Sun Yat-Sen University, Shenzhen 518100, China.
  • Haoxian Lu
    Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China.
  • Beining Zhou
    Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University,Hong Kong 999077, China.
  • Hai Guo
    School of Electrical and Electronic Engineering, Anhui Science and Technology University, Bengbu, China.

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