TY - JOUR
T1 - Hydroxyl Dicarboxylic Acids at a Mountainous Site in Hong Kong
T2 - Formation Mechanisms and Implications for Particle Growth
AU - Li, Hongyong
AU - Lyu, Xiaopu
AU - Xue, Likun
AU - Huo, Yunxi
AU - Chen, Tianshu
AU - Yao, Dawen
AU - Lu, Haoxian
AU - Zhou, Beining
AU - Guo, Hai
N1 - Funding Information:
This study was supported by the Hong Kong Research Grants Council (RGC) via the General Research Fund (HKBU 15219621 and HKBU 15209223), the National Natural Science Foundation of China/RGC joint research scheme (N_PolyU530/20), and the National Natural Science Foundation of China (grant no. 42061160478). We acknowledge Prof. Tao Wang at The Hong Kong Polytechnic University for providing the SMPS data at Hok Tsui.
Publisher Copyright:
© 2025 The Authors. Published by American Chemical Society.
PY - 2025/5/21
Y1 - 2025/5/21
N2 - 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-3) than in the continental air (7.5 ± 1.4 ng m-3). 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 (Ox) 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 Ox. 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.
AB - 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-3) than in the continental air (7.5 ± 1.4 ng m-3). 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 (Ox) 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 Ox. 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.
KW - formation mechanism
KW - hydroxyl dicarboxylic acid
KW - machine learning
KW - malic acid
KW - secondary organic aerosol
UR - http://www.scopus.com/inward/record.url?scp=86000739076&partnerID=8YFLogxK
U2 - 10.1021/acsenvironau.4c00119
DO - 10.1021/acsenvironau.4c00119
M3 - Journal article
C2 - 40416840
AN - SCOPUS:86000739076
SN - 2694-2518
VL - 5
SP - 277
EP - 286
JO - ACS Environmental Au
JF - ACS Environmental Au
IS - 3
ER -
