Aqueous-phase formation of N-containing secondary organic compounds affected by the ionic strength

Gan，Yuqi1,2; Lu，Xiaohui1,3; Chen，Shaodong1; Jiang，Xinghua1; Yang，Shanye1; Ma，Xiewen1; Li，Mei4; Yang，Fan5; Shi，Yewen6; Wang，Xiaofei1,2

2024-04-01

10.1016/j.jes.2023.03.003

Journal of Environmental Sciences (China)   Impact Factor & Quartile

1001-0742

1878-7320

The reaction of carbonyl-to-imine/hemiaminal conversion in the atmospheric aqueous phase is a critical pathway to produce the light-absorbing N-containing secondary organic compounds (SOC). The formation mechanism of these compounds has been wildly investigated in bulk solutions with a low ionic strength. However, the ionic strength in the aqueous phase of the polluted atmosphere may be higher. It is still unclear whether and to what extent the inorganic ions can affect the SOC formation. Here we prepared the bulk solution with certain ionic strength, in which glyoxal and ammonium were mixed to mimic the aqueous-phase reaction. Molecular characterization by High-resolution Mass Spectrometry was performed to identify the N-containing products, and the light absorption of the mixtures was measured by ultraviolet-visible spectroscopy. Thirty-nine N-containing compounds were identified and divided into four categories (N-heterocyclic chromophores, high-molecular-weight compounds with N-heterocycle, aliphatic imines/hemiaminals, and the unclassified). It was observed that the longer reaction time and higher ionic strength led to the formation of more N-heterocyclic chromophores and the increasing of the light-absorbance of the mixture. The added inorganic ions were proposed to make the aqueous phase somewhat viscous so that the molecules were prone to undergo consecutive and intramolecular reactions to form the heterocycles. In general, this study revealed that the enhanced ionic strength and prolonged reaction time had the promotion effect on the light-absorbing SOC formation. It implies that the aldehyde-derived aqueous-phase SOC would contribute more light-absorbing particulate matter in the industrial or populated area where inorganic ions are abundant.

Aqueous-phase reaction Brown carbon Carbonyl-to-imine/hemiaminal Heterocyclic Ionic strength Mass spectrometry

English

Corresponding

National Natural Science Foundation of China[21906024];National Natural Science Foundation of China[21976034];National Natural Science Foundation of China[42077193];National Natural Science Foundation of China[92044301];

2-s2.0-85152144745

Scopus

1.Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention,Department of Environmental Science and Engineering,Fudan University,Shanghai,200433,China
2.Shanghai Institute of Pollution Control and Ecological Security,Shanghai,200092,China
3.Guangdong Provincial Observation and Research Station for Coastal Atmosphere and Climate of the Great Bay Area,Southern University of Science and Technology,Shenzhen,518055,China
4.Institute of Mass Spectrometry and Atmospheric Environment,Guangdong Provincial Engineering Research Center for On-line Source Apportionment System of Air Pollution,Jinan University,Guangzhou,China
5.Environmental Monitoring Station of Pudong New District,Shanghai,201200,China
6.Shanghai Municipal Center for Disease Control & Prevention,China

Gan，Yuqi,Lu，Xiaohui,Chen，Shaodong,et al. Aqueous-phase formation of N-containing secondary organic compounds affected by the ionic strength[J]. Journal of Environmental Sciences (China),2024,138:88-101.

Gan，Yuqi.,Lu，Xiaohui.,Chen，Shaodong.,Jiang，Xinghua.,Yang，Shanye.,...&Wang，Xiaofei.(2024).Aqueous-phase formation of N-containing secondary organic compounds affected by the ionic strength.Journal of Environmental Sciences (China),138,88-101.

Gan，Yuqi,et al."Aqueous-phase formation of N-containing secondary organic compounds affected by the ionic strength".Journal of Environmental Sciences (China) 138(2024):88-101.