Transformation of Polychlorinated dibenzo-p-dioxins and Polychlorinated Dibenzofurans in the Environment

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are toxic, mutagenic and carcinogenic, causing great concern in the public. This review analyzes the properties, toxic effects and sources of PCDD/Fs. The distribution in various environmental compartments, including air, water, soil and sediments, are described. Further, the transformation of PCDD/Fs in the environment was emphatically discussed. The result shows that the fate of PCDD/Fs is mainly controlled by their gasparticle distribution behavior. For gas-phase PCDD/Fs, they are primarily depleted by photolysis and reactions with atmospheric oxidants. For particle-phase PCDD/Fs, dry and wet deposition are the effective removal mode. In the water body, the PCDD/Fs will be inclined to deposit in the sediment. Biodegradation may be a possible environment fate for the PCDD/Fs in sediments. Moreover, PCDD/Fs can enter into the atmosphere in the form of volatilization, especially in the summer. In the soil, the PCDD/Fs can be degraded through anaerobic dechlorination and aerobic dioxygenation, as well as by gas exchange across the air-soil interface. It has a strong net volatilized from the soil into the air for the PCDD/Fs with six or fewer chlorine atoms, while the hepta- and octachloroisomers are approached to the main air-soil exchange balance. Keywords: PCDD/Fs, sources, concentrations, dry and wet deposition, photolysis, oxidation degradation, biodegradation.