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Polychlorinated naphthalenes (PCNs) are widespread environmental contaminants because of their previous usages as lubricants, wood preservatives, plasticizers, and as by-product in technical synthesis of PCBs, metal refining, pulp industry, and municipal waste incinerations, etc, although PCN production and use are thought to have ceased in most countries (Falandysz, 1998; Bidleman et al. , 2010). Even though PCNs partition mostly in soil and sediments in the environment, atmospheric transport represents the primary distribution pathway moving PCNs from the emission sources to terrestrial and aquatic ecosystems. The measured atmospheric concentrations for PCNs were usually on the orders of 10+1 pg m-3, and the PCNs were usually dominant by Tri-CNs and Tetra-CNs (Harner and Bidleman, 1997; Manodori et al. , 2006; Li et al. , 2012). With the vapor pressures of ~3. 6 Pascal for Mono-CNs, ~10-2 Pascal for Tetra-CNs, and ~6 × 10-5 Pascal for Octa-CN at 298 K (Lei et al. , 1999; Puzyn and Falandysz, 2005), the atmospheric PCNs are expected to partition appreciably in gas phase. Field measurements on the atmospheric PCNs indeed found that PCNs up to Hepta-CNs exist as gaseous form, and only 30% of Octa-CN is partitioned in the particulate matter at total PCN levels of tens of pg m-3 (Ohura et al. , 2008). During transport, the gas phase PCNs can be removed from the atmosphere by reactions or deposition, where the reaction removal is due to their reaction with OH radical and O3 and the resulted products may have different hydrophilicity or toxicity. Rate constants of naphthalene with OH and NO3 have been measured as (24. 2 ± 1. 9) × 10-12 and < 3 × 10-17 cm3 molecule-1 s-1 (Atkinson et al. , 1984; Pitts et al. , 1985), and the OH radical reaction is expected to dominant under most atmospheric conditions (Sasaki et al. , 1997). However, no previous study is available for chlorinated naphthalenes. Alternatively, lifetimes of PCNs are predicted using a QSPR-based estimation (Puzyn et al. , 2008). On the other hand, studies are available to a few less volatile chlorinated dibenzo-pdioxines, dibenzofurans, and biphenyls, etc. In this study, the reactions of PCNs with OH radical are investigated using quantum chemistry calculations, and the atmospheric lifetimes and the possible products are predicted. Results for the atmospheric oxidation of PCDDs will also be discussed.