ORIGINAL RESEARCH
Experimental Study on Composition and Optic
of Secondary Organic Aerosol Generated
by Aqueous Photoxidation of Toluene
in Presence of Copper Ions
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1
Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology, College of Chemistry
& Chemical Engineering and Environment, Minnan Normal University, Zhangzhou 363000, China
2
Laboratory of Atmospheric Physico-Chemistry, Anhui Institute of Optics and Fine Mechanics,
Chinese Academy of Sciences, Hefei 230031, China
Submission date: 2023-09-22
Final revision date: 2024-03-01
Acceptance date: 2024-03-29
Online publication date: 2024-07-02
Corresponding author
Mingqiang Huang
Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology, College of Chemistry
& Chemical Engineering and Environment, Minnan Normal University, Zhangzhou 363000, China
Weijun Zhang
Laboratory of Atmospheric Physico-Chemistry, Anhui Institute of Optics and Fine Mechanics,
Chinese Academy of Sciences, Hefei 230031, China
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ABSTRACT
Toluene and other aromatics can dissolve in atmospheric aqueous phases and undergo photooxidation
reactions, forming secondary organic aerosol (SOA) after water evaporation. Copper ion is a typical
heavy metal ion and is able to change the composition and optics of SOA. The reaction solution for
OH-initiated photooxidation of toluene in presence of copper ions is atomized by TSI 9302, and the
water is absorbed by silica gel to simulate the formation of aqueous SOA particles in this study. The
composition and optics of the formed aqueous SOA are on-line and off-line, characterized by mass
spectrometry and spectroscopy. Experimental results demonstrate that laser desorption/ionization
mass spectra for aqueous SOA contain molecular ion peaks at m/z = 108, 124, and 140 for cresol,
mehtyl dihydroxybenzene, and methyl trihydroxybenzene. The absorption peak intensity of phenolic
compounds at 277 nm in the UV-Vis spectra of the collection solution for aqueous SOA increases, and
electrospray ionization negative ion mass spectra show the polymer ion peak as high as m/z = 641. These
indicate that copper ions catalyze the production of more phenolic compounds and hydroxyphenyl ether
polymers formed by the polymerization of cresol. These products have the capacity for strong light
absorption, leading to a significant increase in the averaged mass absorption coefficient () in
200-600 nm for aqueous SOA, which gently rises with an increment of copper ions. These provide the
basis for studying the components and optics of aqueous SOA in presence of heavy metal ions.