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Evidence Proves Essential Role of O2-bridged Bicyclic Compounds in Formation of Secondary Organic Aerosol

Jan 10, 2022 | By LIN Xiaoxiao, ZHAO Weiwei

Volatile organic compounds (VOCs) are important precursors for SOA formation. As a significant aromatic compound of VOCs, 1,3,5-trimethylbenzene (1,3,5-TMB, C9H12) has been attracting much attention. It’s mostly emitted from automobile exhaust, solvent use and industry. In the atmosphere, the oxidation reaction of 1,3,5-trimethylbenzene is mainly initiated by OH radicals.

Recently, research conducted by Prof. ZHANG Weijun’s team at Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS), proved that the O2-bridged bicyclic peroxy radicals is very important reaction intermediate in the oxidation of 1,3,5-TMB.

They found that the reactions can lead to the high mass bicyclic products with a low volatility, and play an essential role in the formation of Secondary Organic Aerosol (SOA).

The result was published in Atmospheric Environment.

The research team detected the chemical composition of the SOA from the oxidation reaction of 1,3,5-TMB with a home-made vacuum ultraviolet (VUV) photoionization aerosol mass spectrometer.

They clearly observed the high-mass O2-bridged bicyclic products in the particle phase with the aid of the deuterated experiments.

"Combined with theoretical study, the formation mechanism of the O2-bridged bicyclic compounds have been illuminated", explained LIN Xiaoxiao, first author of the paper.

Their results gave direct evidences of the essential role of peroxy radical chemistry in the SOA formation.

The work was supported by the National Natural Science Foundation of China, the International Partnership Program of Chinese Academy of Sciences and the Key Program of Research and Development of Hefei Science Center, CAS.

Fig. 1 The major reaction routes of the OH initiated photo-oxidation of 1,3,5-TMB under NOx free conditions. (Image by LIN Xiaoxiao)

Fig. 2 The major reaction routes of the OH initiated photo-oxidation of 1,3,5-TMB under NOx free conditions. (Image by LIN Xiaoxiao)

 

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