Methyl-hydroxy-cyclohexadienyl radicals(OTAs)are the key products of the photooxida-tion of toluene,with implications for the fate of toluene.Hence,we investigated the pho-tooxidation mechanisms and kinetics of three main OTAs(o-OTA,m-OTA,and p-OTA)with NO2 using quantum chemical calculations as well as the fate of OTAs under the different concentration ratios of NO2 and O2.The mechanism results show that the pathway of H-abstraction by NO2 to anti-HONO(anti-H-abstraction)is more favorable than the syn-H-abstraction pathway,because the strong interaction between OTAs and NO2 is formed in the transition states of the anti-H-abstraction pathways.The branching ratios of the anti-H-abstraction pathways are more than 99％in the temperature range of 216-298 K.The total rate constant of the OTA-NO2 reaction is 9.9×10-12 cm3/(molecule·sec)at 298 K,which is contributed about 90％by o-OTA+NO2,and the main products are o-cresol and anti-HONO.The half-lives of the OTA-NO2 reaction in some polluted areas of China are 35 times longer than those of the OTA-O2 reaction.In the atmosphere,the NO2-and O2-initiated reactions of OTAs have the same ability to form cresols as[NO2]is up to 142.1 ppmV,which is impos-sible to achieve.It implies that under the experimental condition,the[NO2]/[O2]should be controlled to be less than 7.8×10-5 to simulate real atmospheric oxidation of toluene.Our results reveal that for the photooxidation of toluene,the yield of cresol is not affected by the concentration of NO2 under the atmospheric environment.

Baocong Zhao;Yongpeng Ji;Dandan Qin;Yuemeng Ji;Jiangyao Chen;Taicheng An

Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control,Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health,Institute of Environmental Health and Pollution control,Guangdong University of Technology,Guangzhou 510006,China;Key Laboratory of City Cluster Environmental Safety and Green development,Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control,School of Environmental Science and Engineering,Guangdong University of Technology,Guangzhou 510006,China

环境科学学报（英文版）

[1]Baocong Zhao;Yongpeng Ji;Dandan Qin;Yuemeng Ji;Jiangyao Chen;Taicheng An-.Competing pathways of cresol formation in toluene photooxidation:OH-toluene adducts react with NO2 or with O2?)[J].环境科学学报（英文版）,2022(04):211-220

photooxidation,cyclohexadienyl,OTAs,photooxida,tooxidation,OTA+NO2,cresols,ppmV,impos

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