Further study on the photochemistry of non-ortho substituted PCBs by UV irradiation in alkaline 2-propanol Yuan Yao a,1 , Kohji Kakimoto a , Hiroaki I. Ogawa a , Yasuhiko Kato a, * , Kiwao Kadokami b , Ryota Shinohara c a Department of Applied Chemistry, Faculty of Engineering, Kyushu Institute of Technology, 1-1 Sensuicho, Tobata, Kitakyushu 804-8550, Japan b Aqua Research Center, Kitakyushu City Institute of Environmental Sciences, 1-2-1 Shinike, Tobata, Kitakyushu 804-0082, Japan c Environmental Conservation Department, Kitakyushu City Environment Bureau, 1-1 Jonai, Kokurakita, Kitakyushu 803-8501, Japan Abstract The photochemical behaviors of six non-ortho substituted PCB congeners, i.e., 3,4-DiCB, 3,5-DiCB, 3,3 0 ,5-TriCB, 3,4,5-TriCB, 3,3 0 ,4,5-TetraCB, and 3,4,4 0 ,5-TetraCB, irradiated at 254 nm in alkaline 2-propanol were investigated. Besides the determination of the photodechlorination pathways of these compounds, the presence of photorear- rangement was observed in the case of 3, 4-DiCB with its products being identi®ed. The results indicate that dechlo- rination is much more important than rearrangement during the process of PCB photolysis. Ó 2000 Elsevier Science Ltd. All rights reserved. Keywords: Non-ortho substituted PCBs; Photodechlorination pathway; Photorearrangement pathway; UV irradiation 1. Introduction Safe and Hutzinger ®rst reported a laboratory study on the photolysis of polychlorinated biphenyls (PCBs) in 1971. They irradiated 2,2 0 ,4,4 0 ,6,6 0 -HexaCB in hexane and methanol separately at 310 nm and found that the compound was photolyzed to form products through dechlorination and other photochemical reactions (Safe and Hutzinger, 1971). Since that time, many publica- tions dealing with the photochemical behaviors of these compounds have been published. Bunce et al. studied the impact of solar degradation of PCBs in the aquatic environment and concluded that photodegradation of PCBs exhibits an environmental signi®cance (Bunce et al., 1978a). Due to the low solubility of PCBs in water, various organic solvents such as hexane (Herring et al., 1972; Ruzo et al., 1972; Miao et al., 1996), cyclohexane (Ruzo et al., 1974, 1975), iso-octane (Bunce et al., 1978b), benzene (Herring et al., 1972), and alcohols (Nishiwaki et al., 1972, 1973, 1979; Nordblom and Miller, 1974; Ruzo et al., 1974; Hawari et al., 1991; Grittini et al., 1995) have been employed in PCB pho- tochemical studies. It has been shown that the photo- reaction rate of these compounds is faster in hydroxylic solvents than in nonpolar solvents. In the case of using alkaline alcoholic solution, 2-propanol possessing an active hydrogen at a-position provides the highest de- composition yield (Nishiwaki et al., 1973; Hawari et al., 1992). As most PCB congeners do not strongly absorb wavelength above 300 nm, a number of investigations have utilized low-pressure mercury lamps (k max  254 nm) as the light sources (Ruzo et al., 1974; Bunce et al., 1978b; Lepine et al., 1991; Hawari et al., 1992). In the meantime, various photosensitizers have been applied in the transfer of light energy to the PCB molecules to Chemosphere 40 (2000) 951±956 * Corresponding author. E-mail address: yao@kan.ynu.ac.jp (Y. Yao). 1 Present address: Institute of Environmental Science and Technology, Yokohama National University, 79-7 Tokiwadai, Hodogaya, Yokohama 240-8501, Japan. 0045-6535/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 5 - 6 5 3 5 ( 9 9 ) 0 0 3 3 8 - 0