Please cite this article in press as: Meng, Q., et al. Particle size distribution and characteristics of polycyclic aromatic hydrocarbons during a heavy haze episode in Nanjing, China. Particuology (2014), http://dx.doi.org/10.1016/j.partic.2014.03.010 ARTICLE IN PRESS G Model PARTIC-671; No. of Pages 8 Particuology xxx (2014) xxx–xxx Contents lists available at ScienceDirect Particuology jo ur nal home page: www.elsevier.com/locate/partic Particle size distribution and characteristics of polycyclic aromatic hydrocarbons during a heavy haze episode in Nanjing, China Qingzi Meng a,b , Shuxian Fan a,b,∗ , Jiabao He b , Jian Zhang b , Yu Sun b , Yue Zhang b , Fan Zu c a Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing 210044, China b Department of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044, China c Jiangsu Institute of Meteorological Sciences, Nanjing 210008, China a r t i c l e i n f o Article history: Received 15 December 2013 Received in revised form 25 February 2014 Accepted 5 March 2014 Keywords: Polycyclic aromatic hydrocarbons Agricultural burning Haze episode Particle size distribution Meteorological conditions Nanjing a b s t r a c t A heavy haze episode caused by agricultural burning occurred in Nanjing from November 7 to November 8, 2009. PM 10 samples were collected on normal and hazy days from November 1 to November 14, 2009 at both city and suburban sites of Nanjing. Sixteen PAHs were measured during the day and at night. The results show that the concentrations of the particles were as high as 579.55 and 573.43 g/m 3 during the haze episode at the city and suburban sites, respectively, 3–4 times higher than those on a normal day. The proportions of fine particles during the haze episode were also higher than those on a normal day. The changes in the concentrations of PAHs were in accordance with the concentrations of the particles. High- molecular-weight PAHs composed approximately 80% of the total PAHs on normal days and during the haze episode. The concentration of PAHs in fine fractions significantly increased during the haze episode, and this increase was most obvious at night at the city site. The proportion of total carcinogenic PAHs in fine particles was relatively high during the haze episode at both sampling sites, particularly at night at the city site. © 2014 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Introduction Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants that are ubiquitous in urban and sub- urban atmospheres. Atmospheric PAHs are partitioned between the gaseous phase and the particulate phase; the latter are called particle-bound polycyclic aromatic hydrocarbons (pPAHs). Although atmospheric PAHs are partitioned between two phases, PAHs are predominantly associated with particulate matter. pPAHs are a significant danger to human health through inhalation (Chetwittayachan, Shimazaki, & Yamamoto, 2002). Many PAHs have mutagenic and carcinogenic properties, and the hazard posed by these compounds increases as their molecular weight increases (Tsai et al., 2004). PAHs are primarily derived from the imperfect combustion processes of mobile sources (vehicular emissions) and ∗ Corresponding author at: Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing 210044, China. E-mail addresses: shuxianf@nuist.edu.cn, mengqingzi@163.com (S. Fan). of stationary sources (industries) (Ravindra, Sokhi, & van Grieken, 2008). Haze is defined by relative humidity <80%, by visibility <10 km and by the concentration of particles when the relative humidity is between 80% and 95%. Haze is called as a heavy haze episode when the visibility is lower than 2 km (Wu et al., 2010). Haze is generally believed to be related to atmospheric particulate matter (Chan & Yao, 2008). Recent studies also showed that haze not only damages human health but also is important for the global energy balance (Huang, Yuan, Wang, & Wang, 2011; Menon, Hansen, Nazarenko, & Luo, 2002; Tao et al., 2009). There have been many studies con- cerning pPAHs in large cities in China, including Guangzhou (Tan et al., 2006, 2009a, 2009b), Shanghai (Cheng et al., 2007), Dalian (Kong et al., 2011; Tian et al., 2009), Hong Kong (Guo, Lee, Ho, Wang, & Zou, 2003), Fuzhou (Zhang et al., 2013), Xiamen (Hong, Yin, Wang, & Ye, 2007), Beijing (Liu, Gao, & An, 2008), and Nan- jing (Wang, Huang, Zhao, Niu, & Dai, 2006). These authors found that the concentrations of PAHs were closely related to the sizes of atmospheric particles. Concentrated in the respirable size range of 0.1–1 m, the burning of fossil fuels is the most important emission source of PAHs. Some studies also found that the main influenc- ing factors of the concentration of pPAHs were emission sources http://dx.doi.org/10.1016/j.partic.2014.03.010 1674-2001/© 2014 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.