Ambient volatile organic compounds (VOCs) concentrations measured in Bangkok and its suburb in Thailand were estimated for their secondary organic aerosol formation potential (SOAP) to elucidate the major compounds contributing to the formation of secondary fine particulates. VOCs were collected to evacuated canisters and analyzed by Gas Chromatography - Mass Spectrophotometer (GC-MS) in accordance with US-EPA TO15. Measured data from January 2013 to December 2019 were used in this study. The results indicate that the top five species of VOCs contributing to SOAP were toluene (66-54%), m- ,p-xylene (11-7%), ethylbenzene (9-8%), benzene (12-5%), o-xylene (5-4%) and styrene (9-4%), in rank order. These VOCs accounted for more than 90 % of total SOAP. Positive Matrix Factorization (PMF) was then used to identify the potential emission sources of these compounds. The results clearly indicated a high contribution from mobile sources at roadside monitoring stations. As for the suburban area, most of the total VOC concentrations were from mobile source emissions, chemical use in the households, and open burning. The results of this study highlight the necessity to control these emission groups to reduce the formation potentiality of secondary organic aerosols and PM2.5 pollution.
