Laser desorption/ionization mass spectrometric study of secondary organic aerosol formed from the photooxidation of aromatics |
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| Authors: | Mingqiang Huang Weijun Zhang Liqing Hao Zhenya Wang Wenwu Zhao Xuejun Gu Xiaoyong Guo Xianyun Liu Bo Long Li Fang |
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| Institution: | (1) Laboratory of Environment Spectroscopy, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, 230031, People’s Republic of China |
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| Abstract: | Five aromatic hydrocarbons – benzene, toluene, ethylbenzene, p-xylene and 1,2,4-trimethylbenzene – were selected to investigate the laser desorption/ionization mass spectra of secondary
organic aerosols (SOA) resulting from OH-initiated photooxidation of aromatic compounds. The experiments were conducted by
irradiating aromatic hydrocarbon/CH3ONO/NO
X
mixtures in a home-made smog chamber. The aerosol time-of-flight mass spectrometer (ATOFMS) was used to measure the aerodynamic
size and chemical composition of individual secondary organic aerosol particles in real-time. Experimental results showed
that aerosol created by aromatics photooxidation is predominantly in the form of fine particles, which have diameters less
than 2.5 μm (i.e. PM2.5), and different aromatic hydrocarbons SOA mass spectra have eight same positive laser desorption/ionization
mass spectra peaks: m/z = 18, 29, 43, 44, 46, 57, 67, 77. These mass spectra peaks may come from the fragment ions of the
SOA products: oxo-carboxylic acids, aldehydes and ketones, nitrogenated organic compounds, furanoid and aromatic compounds.
The possible reaction mechanisms leading to these products were also discussed. |
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| Keywords: | Aromatic hydrocarbons Secondary organic aerosols Smog chamber Laser desorption/ionization Reaction mechanism |
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