BIT has made important progress in the study of the growth mechanism of Marine aerosol

News Source: Zhang Xiuhui, School of Chemistry and Chemical Engineering

Translator: Wang Yuhao; News Agency of BIT


Recently, the team of Professor Zhang Xiuhui, School of Chemistry and Chemical Engineering, Beijing Institute of Technology/Key Laboratory of Atomic and Molecular Cluster Science, Ministry of Education, in collaboration with the team of researcher He Hong, Center for Ecological Environment, Chinese Academy of Sciences, and the team of Professor Joseph S. Francisco, University of Pennsylvania, has made important progress in the study of the growth mechanism of Marine aerosols. The relevant research results are entitled "Chemical Implications of Rapid Reactive Absorption of I2O4 at the Air-Water Interface". It was published in the Journal of the American Chemical Society (JACS), a top international chemistry journal (DOI: 10.1021/ JACS.3C01862). This work is based on the BIT as the first communication unit, and Professor Zhang Xiuhui, Researcher He Hong and Professor Joseph S. Francisco are co-corresponding authors. Ning An, postdoctoral fellow at the School of Chemistry and Chemical Engineering at BIT, and Professor Zhong Jie from the China University of Petroleum are co-first authors of the paper.

Marine aerosols constitute the largest natural source aerosol system in the world, which has an important impact on global radiation balance, climate change and even people's life. Although studies have shown that iodine-containing substances are closely related to the formation of Marine aerosols, the mechanism of aerosol growth involved in iodine-containing substances remains unclear. Laboratory studies have shown that iodide (I x O y) is an important component of aerosol particle formation (of which the concentration of I2O4 is the highest). However, the main iodine group of aerosol particles detected in the field is IO3- ion, but no iodine oxide is detected. The discrepancy between laboratory and field observations is difficult to explain in terms of current chemical reaction mechanisms, which greatly limits the understanding of how iodine oxides affect Marine aerosol formation.

The heterogeneous reaction mechanism at the gas-liquid interface (i.e. liquid aerosol surface) of I2O4 under the influence of sulfuric acid and amines in the atmosphere, revealed by Professor Zhang Xiuhui and his team at the BIT and his collaborators through a combination of quantum chemistry calculation and first-principles molecular dynamics simulation, can better explain the above divergence problems. Because the chemical components in the real atmosphere are far more complex than the "simple" experimental environment, in addition to iodine oxides, there are also pollutants such as sulfuric acid, and amines generated by Marine organisms. Their collaborative study found that I2O4, with the participation of sulfuric acid and organic amines, can react rapidly (picosecond level) at the aerosol gas-liquid interface (Figure 1) to generate HIO2 iodate and a series of ionic products, such as HSO4-, IO3-, DMAH+, etc. The resulting reaction products can be combined into larger complexes by hydrogen, halogen and ionic bonds, thus limiting their diffusion to the droplet phase. At the same time, the interfacial water molecules bind to the product molecules by hydrogen bonding, making it difficult to evaporate into the gas phase (Figure 2). In addition, the above products attached to the surface of the droplets (IO3-/DMAH+, etc.) have lower volatility and higher hygroscopic properties than the reactants (I2O4/DMA, etc.) (Figure 3), and can also promote the hygroscopic growth of aerosols.


Figure 1. Gas-liquid interface reaction mechanism of I2O4 under the influence of sulfuric acid and organic amine


Figure 2. Gas-liquid interface reaction product of I2O4


Figure 3. Hydration distribution of I2O4 reactants/products at gas-liquid interface

In conclusion, the mechanism of I2O4 reaction at aerosol gas-liquid interface under the influence of sulfuric acid and organic amines revealed in this study not only explains the divergence between laboratory and field observations, but also helps to understand the heterogeneous reaction process of iodine chemistry and its influence on aerosol growth. At the same time, new sources of important components such as HSO4-/IO3- in Marine aerosols were revealed, which provided theoretical clues for further understanding of the relationship between Marine atmospheric iodine chemistry and aerosol formation.

The research was supported by the National Science Foundation for Outstanding Young People (22225607) and the National Natural Science Foundation (21976015 and 22188102).

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About the author:

Zhang Xiuhui, professor of Beijing Institute of Technology, doctoral supervisor, winner of the National Outstanding Youth Science Fund. In 2007, he graduated from BIT and was nominated for one hundred outstanding doctoral dissertations in China. He is mainly engaged in theoretical research on the formation mechanism of atmospheric particulate matter, and has published more than 60 SCI papers in J. Am. Chem.Soc., Angew.Chem.Int.Ed., Proc.Natl.Acad.Sci.USA and other journals as the corresponding or first author. As the third, he won the second prize of Natural Science of the Ministry of Education and the second prize of science and Technology of China North Weapons Group Corporation. One doctoral student was awarded the outstanding doctoral thesis of the Chinese Particulate Matter Society.