Mechanism and kinetic study on the OH-initiated degradation of 2,3,7,8-tetrachlorinated dibenzofuran in atmosphere.

High-accuracy molecular orbital calculation has been performed to investigate the atmospheric oxidation reaction of 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TeCDF) initiated by the OH radical in the presence of O(2) and NO/H(2)O. The possible channels involved in the reaction are discussed, and the favorable reaction pathways are revealed. The degradation occurs easily once the OH radical initiates the reaction. Two aspects need to be mentioned: one is that H(2)O in atmosphere is a source of OH radical which will initiate a new round of degradation and improve the degradation efficiency; the other is that the furan ring of 2,3,7,8-TeCDF can be turned into dioxin ring, which may explain the experimental hypothesis that polychlorodibenzofurans can be transformed to polychlorodibenzo-p-dioxins. Rate constants of the elementary reactions are calculated over a temperature range of 250-400K. Arrhenius formulas are fitted and the atmospheric lifetimes of reaction species in the troposphere are discussed for the first time, which can be applied to the study on the model simulation and the management of the hazardous materials.