Study On The Partitioning And Speciation Of Elements From Municipal Solid Waste Incineration And Their Environmental Effects By Synchrotron Techniques

The rapid development of urbanization has led to more and more emissions of municipal solid waste(MSW). Waste incineration has become a trend dealing with waste and is vigorously promoted in China for its large capacity of reducing waste and high efficiency of recycling. However, secondary pollution such as heavy metals and acid gases brought by the waste incineration cannot be ignored. Synchrotron radiation technology is an effective means to analyze complex environmental samples because of its low detection limit, high precision and non-destructive in situ performance. In this study, by using synchrotron radiation X-ray fluorescence technique(SRXRF) and synchrotron radiation X-ray absorption near-edge structure(XANES) and several traditional laboratory techniques, the content and transformation of elements in the emissions from the incineration plant were studied, the characterization, source origin and cytotoxicity of atmospheric particles(sampled at the flue gas deposition of the municipal solid waste incineration plant, the same as follow) were analyzed and the impact of particulate matter from the incineration on the surrounding atmospheric environment was assessed.Sulfur and chlorine has an important impact on the transformation of heavy metals in the incineration process and harmless dealing with the products of incineration. In this paper, the speciation of sulfur and chlorine in raw waste(kitchen waste), incinerated products(fly ash and bottom ash) as well as in atmospheric particles were analyzed using XANES, the element concentrations in those samples were analyzed using SRXRF and ICP-MS. The results showed that the sulfur was mainly in stable state as sulfate in the raw waste, fly ash and bottom ash with an atomic percentage of 49%, 72% and 96%, respectively. There was a certain amount of organic sulfur in the raw waste and about 26 % of the sulfur presented in the form of sulfite in the fly ash. SO2, generated in the combustion of sulfur in waste, can be absorbed by the lime slurry used as dedusting agent and be transformed into sulfite in the fly ash. The XANES spectra of chlorine in the incinerated products showed that it was mainly in-1 state in the incineration products. Sulfur was mainly in sulfate state in size-segregated atmospheric particles, however, there was some organic sulfur of low valence state in the coarse particles. Such distribution may be related to the origination of sulfur pollution and the formation process of particulate matter. The XANES spectra of Pb in the incinerated products showed that it was mainly in PbCl2, Pb3O4, PbS and PbO. Chlorine content in the fly ash was much higher than that in the bottom ash, but no significant difference in the distribution of sulfur, it is because that the volatility of metal chlorides was usually higher than that of metal oxide and metal sulfide. Most of the concentration of metal elements in fly ash is higher than those in bottom ash. Pb, Cd significantly enriched in the fly ash, the enrichment factor suggested that Pb, Cd, Cu and Zn were extremely polluted. Micro element scanning of fly ash and bottom ash showed that the each distribution of Pb, Zn, Cu, Cr, Fe and Mn on fly ash and bottom ash particles was inhomogeneous and had a significant local enrichment. The element transformation during the incineration process was related to the characteristic of element itself and the the combustion conditions.The mass size distributions of atmospheric particles colletced around the MSW plant using a l3 low pressure cascade impactor showed that fine particles were the major part in the atmospheric particles, took about 72.9% of the total mass. The crust elements were enriched in coarse particles while the anthropogenic elements were enriched in fine particles. Pb, Zn and Cd were highly associated with the incinerator emissions. Biological experiments revealed that all the coarse, fine and ultrafine particles surround the incineration plant can reduce cell viability. The toxicity of fine particles and ultrafine particles was higher than that of coarse particles. Particles toxicity depended on chemical composition and particle size, higher content of metal elements(in particular the toxic metals elements) and smaller particle size can both cause higher toxicity.The results of this study can provide relevant theoretical and experimental basis for assessing the impact of municipal solid waste incineration emissions on the surrounding environment.