| Unintended production of persistent organic pollutants?UP-POPs?mainly comes from solid waste incineration,metal smelting,metal regeneration and other thermal related industries.Different heat-related industries use different raw materials,thermal treatment processes,flue gas purification technologies,etc.,resulting in different types and contents of pollutants discharged.The existing data mainly focus on PCDD/Fs,while the lack of information about other UP-POPs,such as PBDD/Fs,PBCDD/Fs and PBDEs is not conducive to pollution control.In order to further clarify the emission characteristics of UP-POPs in various thermal related industrial flue gases and the impact on the surrounding environment,this paper selected seven enterprises with different technology and treatment types as the research object.The concentration level,distribution characteristics and influencing factors of PCDD/Fs,PBDD/Fs,PBCDD/Fs and PBDEs in flue gas were studied systematically;The trend and source of PCDD/Fs in different incineration stages of the two most common municipal solid waste incineration systems were studied.At the same time,the existing level and characteristics of PCDD/Fs in the atmosphere around municipal solid waste incineration plant are analyzed.The main results are as follows:?1?A variety of UP-POPs?17 kinds of PCDD/Fs,14 kinds of PBDD/Fs,12 kinds of PBCDD/Fs and 18 kinds of PBDEs?were identified and quantified by high resolution gas chromatography and high resolution mass spectrometry?HRGC/HRMS?,which filled up the blank of the source data of PBCDD/Fs and PBDD/Fs in China.The results showed that the target compounds were detected in all flue gas samples.The total mass concentration and total toxic equivalent concentration range were 8.50×105?9.55×concentration level of each enterprise is HWI>IWI>Medical WI>SCu>SNT>MWI-1>MWI-2.The order of average toxic equivalent concentration was IWI>SCu>SNT>Medical WI>HWI>MWI-2>MWI-1.The composition of the target substances in the flue gas emitted by different types of enterprises is different.In general,?Cl47CDFs and?Cl78CDDS,1,2,3,4,6,7,8-Hp BDF,1-B-2,3,7,8-Te CDD and2-B-1,3,7,8-Te CDD,BDE209 and BDE183 are the main monomers of PCDD/Fs,PBDD/Fs,PBCDD/Fs and PBDEs,respectively.It is also found that the types of raw materials or incineration materials have a great impact on the UP-POPs emission level of various thermal related industries,and the optimization of raw materials can effectively reduce pollution emissions.?2?Through the analysis of fly ash samples in different stages,the trend and source of PCDD/Fs in different stages of grate furnace and CFB MSW incineration were further clarified.It is found that the distribution characteristics of PCDD/Fs from two kinds of incinerators are quite different,but their concentrations show the same trend,that is,medium temperature economizer stage>low-temperature bag filter stage>high-temperature incineration stage.This may be due to the large amount of PCDD/Fs generated by precursor reaction or de novo reaction in the middle temperature economizer stage.According to the principal component analysis?PCA?,the correlation of PCDD/Fs of grate furnace and fluidized bed municipal solid waste incinerator in the high-temperature incineration stage is relatively high,and the PCDD/Fs mainly comes from the PCDD/Fs which is not completely decomposed in the original waste.These results provide methods and ideas for more effective control of PCDD/Fs pollutants in the process of waste incineration.?3?In this paper,passive sampling technology is used to collect atmospheric samples and 17 kinds of PCDD/Fs in the atmosphere around two kinds of MSW incineration plants were analyzed by HRGC/HRMS.It was found that the range of toxic equivalent concentration was 0.089?0.759 pg TEQ Nm-3 and 0.115?0.408 pg TEQ Nm-3,respectively.2,3,7,8-TCDF,1,2,3,7,8-He CDF and 1,2,3,4,6,7,8-He CDF are the main monomers in the atmosphere near the fluidized bed incineration plant.The atmosphere near the grate incinerator is dominated by 1,2,3,4,6,7,8-He CDF,2,3,4,6,7,8-Hx CDF and?Cl78CDDS,which are similar to the distribution characteristics of PCDD/Fs in the flue gas of the incinerator.The spatial distribution of PCDD/Fs in the atmosphere around the two types of incineration plants is the same.With the increase of distance,the impact of pollutants discharged from the incineration plant on the surrounding atmosphere is gradually weakened,with a larger impact in the range of 500?1000 m and a smaller impact in the range of more than 5000 m.The results provide a scientific basis for the site selection,planning and management of municipal solid waste incineration plant,and are of great significance to eliminate the"Not In My Back Yard".In addition,the concentration of PCDD/Fs increased obviously in the samples with biomass open incineration site,indicating that biomass open incineration is also one of the important sources of PCDD/Fs in the atmosphere. |
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