Characteristics Of Volatile Organic Compounds (VOCs) At The Urban And Suburban Sites In Guangzhou,China

Volatile organic compounds（VOCs）are a common trace gas in the atmosphere.VOCs can generate Ozone（O₃）and secondary organic aerosols（SOA）through complex atmospheric chemical processes,which can cause and intensify regional air pollution.It is of great significance to study the characteristics and effects of VOCs in the atmosphere for the characteristics of air pollution,atmospheric chemical process and pollution prevention and control.From September to November 2017,the online VOCs monitoring system was used to carry out the online observation of atmospheric VOCs at the urban（Modiesha,MDS）and suburban（Wanqingsha,WQS）stations in Guangzhou.The concentration level,species composition and time variation characteristics of the two stations were obtained,and their sources were analyzed to explore the atmospheric chemical process and its contribution to the generation of O₃.The results are as follows:（1）The concentration of total VOCs in the atmosphere of Guangzhou urban site（MDS）ranged from 6.75-184 ppbv（mean value:31.2±22.6 ppbv）,and the concentration of total VOCs in the atmosphere of Guangzhou suburban site（WQS）ranged from 4.43-190 ppbv（mean value:36.3±27.9 ppbv）.（2）In the two environments,alkanes and aromatics are the dominant VOCs groups.However,the dominant VOCs species are different:propane and toluene were the most abundant VOCs species in MDS and WQS,respectively.（3）Based on the results of characteristic ratio method,correlation analysis and air mass back trajectory analysis,the sources of VOCs in the two environments are different.VOCs in the atmosphere of urban site MDS mainly came from traffic emissions.In addition to the long-distance transmission from the upwind region,VOCs in the atmosphere of WQS suburban site are also affected by industrial emissions.（4）The research and analysis of ozone generation potential（OFP）show that the most important contribution to ozone is aromatic hydrocarbons,among which the OFP of alkanes in both sites.MDS has a proportion that can not be ignored.Therefore,it is of great significance to reduce the photochemical formation of O₃ by reducing the traffic emissions in Guangzhou urban areas and reasonably controlling the industrial emissions in the industrial areas around Guangzhou.（5）The PBM-MCM was used to simulate the high O₃ pollution period of WQS.The results show that the high frequency O₃ pollution events in WQS were caused by the transmission of O₃ precursors（such as VOCs and NO_x）and the occurrence of photochemical reactions such as strong O₃ formation.