| Dioxins (PCDD/Fs) are a common name of a group of pollutants that are semi-volatile, bioaccumulative, persistent and toxic. China, as one of the Stockholm International Convention parties, has responsibilities and obligations to define the major source and environmental pollution distribution of POPs, finally aiming to reduce the emission. (1) The monitoring in the non/less developed areas is poor in the present, which are not conducive to the overall status. (2) The stack gas, dust, fly ash and slag are produced from the incineration process of municipal solid waste (MSW), medical waste (MW) and hazardous waste (HW), containing huge quantities of dioxins. It is necessary to investigate PCDD/Fs emission in the different types of incinerators for the formation mechanism, which can provide support for the PCDD/Fs emission reduction.The PCDD/Fs distribution of the different environmental receptors in a typical natural environment was studied, the pollution source of the environmental indicators and human expose health evaluation were qualitatively and quantitatively analyzed by models. The dioxins current emission in different waste incinerators and PCDD/Fs formation mechanisms were studied in this paper. The environmental fates of dioxin are investigated based on a LevelⅢmultimedia fugacity model. The main conclusions are drawn as follows:(1) The dioxin levels of ambient air, tree bark, soil and river sediment samples in the study were 29-55 fg I-TEQ/Nm3,0.46-1.3 pg WHO-TEQ/g,3.2-1.3 pg WHO-TEQ/g, 1.3-1.6 pg WHO-TEQ/g, which showed that the pollution was in the middle level of the world. The high-chlorinated congeners (heptachlor- and octachloro-) were the main characteristic factors, especially the high levels of OCDD in the soil and river sediments. There was no significant industrial pollution in this region. The importance of the tree bark, soil and sediment as the monitoring indicators in environmental receptors was discussed. (2) The receptor models were adopted to apportion the dioxins sources in this area. It suggested that the main pollution resource was the natural formation and agricultural-chemical products, such as pesticides or herbicides. This paper presents a structured evaluation of multi-pathway human exposure model. The result showed that total exposure was 0.4460pg I-TEQ/(kg·d), which means the PCDD/Fs contamination was relatively minor.(3) The emission levels in the most incinerators cannot meet the limit standard of PCDD/Fs emission in China. Estimated annual dioxins emission amount of 9 incinerators is 0.97 ng I-TEQ, in which MSW incineration is the main pollution source. The mechanism was the de novo synthesis, the lack of the emission control equipment will result in the huge number dioxins transferring from incinerators to the environment. PCDD/F homologue can simplify the detection of dioxins in incinerators.(4) The control strategy was described as followed:source control, process control and terminal control. The source separation should be placed on the agenda. The primary objective was to avoid kitchen waste in the incineration. In order to reduce the generation of dioxins, the combustion efficiency should be improved. The key factors in terminal control had two, short the quenching time and remove the dioxin suspended in the gas phase and deposited in the solid phase bound to the fly ash particles.(5) The Level III multimedia fugacity model was used to simulate the environmental fates of dioxin. The simulation showed that the concentration of dioxin in the soil and sediments would not change, but which in air was significantly increased as 26.2,26.3, 26.4 fg TEQ/m3. The major transferring flow of dioxin among environmental medias is from atmosphere to soil and the soil is the largest sink.
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