Atmospheric Environment 40 (2006) 1266–1274 Source identification and size distribution of atmospheric polycyclic aromatic hydrocarbons during rice straw burning period Hsi-Hsien Yang a,Ã , Cheng-Hsien Tsai b , Mu-Rong Chao c , Yi-Ling Su a , Shu-Mei Chien a a Department of Environmental Engineering and Management, Chaoyang University of Technology, No. 168, Jifong E. Rd., Wufong Township, Taichung 41349, Taiwan, ROC b Department of Chemical and Material Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan, ROC c Department of Occupational Safety and Health, Chung Shan Medical University, Taichung 402, Taiwan, ROC Received 29 June 2005; received in revised form 4 October 2005; accepted 14 October 2005 Abstract Atmospheric particulate and polycyclic aromatic hydrocarbon (PAH) size distributions were measured at a suburban area in central Taiwan during the rice straw burning and non-burning periods. Samples were acquired using a semi-volatile sampling train (PS-1 sampler) and a micro-orifice uniform deposit impactor (MOUDI). The collected materials were extracted and then analyzed by gas chromatograph/mass selective detector for 21 PAHs. The average total PAH concentrations of particulate and gaseous phases were 33.0 and 1160 ng m 3 , respectively, in the rice straw burning period, which were higher than those on the non-burning days. Potential sources of PAHs were identified using the characteristic ratios. Benzo[a]pyrene/benzo[ghi]perylene ratio indicates the burning of rice straw is a significant source for PAH contribution at the sampling area. It also suggests that the rice straw burning primarily contribute fine particulate PAHs. Bimodal size distributions are obtained with a predominance of total PAHs in the accumulation mode during rice straw burning periods and in ultra-fine mode during non-burning periods. The particulate and particulate phase PAHs from rice straw burning are coarser than those from vehicle exhaust. The results also suggest that the amounts of PAHs per unit mass of particulate are less for the burning of rice straw than those of vehicle emissions. r 2005 Elsevier Ltd. All rights reserved. Keywords: PAHs; Mass median diameter; Respirable particulate; Biomass burning; Characteristic ratio 1. Introduction Biomass burning has drawn global concerns in the past decades for its effects on visibility, human health and global climate by emitting particulate matters and other gaseous pollutants (Fang et al., 1999; Koe et al., 2001; Abas et al., 2004; Lemieux et al., 2004). It has been estimated that 104 Tg yr 1 is released by biomass burning (Zamperlini et al., 1997). Agricultural field burning is a type of biomass burning which may be regionally important in the harvest season. At harvesting time, from June ARTICLE IN PRESS www.elsevier.com/locate/atmosenv 1352-2310/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2005.10.032 Ã Corresponding author. Tel.: +886 4 23323000x4451; fax: +886 4 23742365. E-mail address: hhyang@mail.cyut.edu.tw (H.-H. Yang).