Identification of volatile organic compounds in suburban Bangkok, Thailand and their potential for ozone formation Jeeranut Suthawaree a, ⁎, Yosuke Tajima a , Alisa Khunchornyakong a , Shungo Kato a , Alice Sharp b , Yoshizumi Kajii a a Department of applied chemistry, Faculty of Urban Environmental Sciences, Tokyo Metropolitan University, 1–1 Minami-Osawa, Hachioji, Tokyo, 192–0397, Japan b Sirindhorn International Institute of Technology, Thammasat University – Rangsit Campus, P.O.Box 22, Pathum Thani, 12121, Thailand article info abstract Article history: Received 9 June 2011 Received in revised form 27 October 2011 Accepted 30 October 2011 Measurement of Volatile Organic Compound (VOC) was carried out in suburban Bangkok during July 2–8, 2008. Analysis was performed using GC-FID and GC-MS. High mixing ratios of VOCs detected during the morning and evening are most likely due to vehicular emissions. Averaged VOC mixing ratios revealed distinct difference between mixing ratios of weekdays and weekend, which the latter were found to be lower. The most abundance species were propane and toluene. Ratios of benzene over toluene suggested that additional toluene mixing ratios was owing to in- dustrial emission, which was particularly larger during weekdays. Comparison between C 2 Cl 4 and CH 3 Cl mixing ratios obtained for suburban Tokyo reveal a relatively lower influence of biomass burning than suburban Bangkok. Elucidating by Ozone Formation Potential, toluene was found to contribute the most to O 3 production followed by ethylene, m-,p-xylene, and propylene. © 2011 Elsevier B.V. All rights reserved. Keywords: Volatile organic compounds Ozone formation potential Suburban Bangkok 1. Introduction Tropospheric Ozone (O 3 ) has long been known as a major component of photochemical smog, deteriorating air quality, affecting human health, and lessening plant productivity. Moreover, surface O 3 is a greenhouse gas. Despite spatial and temporal variations of O 3 and limitations of model simu- lation, its increasing trend has been aggravated with the fact that O 3 is the third largest contributor to an increase in direct radiative forcing (+ 0.35 ± 0.15 W m -2 relative to the level of year 1750) (Intergovernmental Panel on Climate Change (IPCC), 2007). In the atmosphere, in the presence of sufficient solar radiation and major ingredients known as NO x (NO + NO 2 ) and Volatile Organic Compounds (VOCs), O 3 is photochemically generated (Sillman, 1999). The atmospheric lifetime in the troposphere on the order of days and weeks, O 3 can be formed in mega cities as well as downwind suburbs and carried toward rural and remote areas around the world via atmospheric transport pathways (Logan, 1985; Banta et al., 1998; Monks, 2000; Vingarzan, 2004). Thailand is located in the heart of the Southeast Asian region. The population is estimated to be more than 63 million (Department of Provincial Administration (DOPA), 2009) with the densest area in the capital city, Bangkok Metropolitan Area (BMA). Located in a tropical region, Thailand is subjected to ex- cessive tropospheric O 3 production due to the intense emission of air pollution, coupled with year-round sunlight. The Asian Monsoon controls flow patterns of air masses in this region; Continental air masses (from southern China) prevail during the dry season (November to April) and marine air masses from the Indian Ocean prevail during the wet season (May to October). This results in high concentrations during the dry season and low concentrations during the wet season of O 3 and CO observed in the remote areas of Thailand (Pochanart et al., 2001, 2003). Emission inventories of various cities reported by Guttikunda et al. (2005) estimated relatively similar amounts of VOCs emitted in Bangkok and those of East Asian cities, i.e. Beijing and Seoul, while Bangkok emissions are slightly lower than that of Tokyo. More recent study on the comparison of Atmospheric Research 104-105 (2012) 245–254 ⁎ Corresponding author. Tel.: + 81 42 677 2833; fax: + 81 42 677 2837. E-mail address: deutschf@tmu.ac.jp (J. Suthawaree). 0169-8095/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.atmosres.2011.10.019 Contents lists available at SciVerse ScienceDirect Atmospheric Research journal homepage: www.elsevier.com/locate/atmos