Study on the Interaction between Heavy Metals and Organic Matter in Municipal Solid Waste Incineration Residues in Landfill Sites

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It was confirmed that humic substances (HSs) were formed with the range of 200〜1,100 mg/kg-sample in landfills mainly disposed with MSWI residues and with a low content of organic matters. Leaching capacity of organic matter was little affected by pH variation after landfilling, but there was no significant effect of pH for HSs' leaching. Humic acid (HA) and fulvic acid (FA) were also proven to be present in MSWIR landfills leachate. The waste composition strongly influence over the concentration of HSs in leachate. Also the landfill's age influences over the concentration of HSs considering that in time the concentration tend to decrease because of the degradation of HSs. HSs also can be found, especially in SS from leachates originated in landfills with MSWIR. The chemical and spectroscopic characteristics of HSs extracted from landfilled MSWIR were characterized. FT-IR spectra showed the similar results of HSs, and in the case of FA, chemically stronger bond of COOH groups were detected. From the results of CP-MAS ^<13>C-NMR of extracted HSs, it was found that HSs derived from MSWIR have its specific peak shape of NMR spectra, comparing with HSs derived from other origins ; crushed incombustibles, and MSW landfill leachate. From potentiometric titration for FA, it could be concluded that FA has a dissociation property as a high-polymer electrolyte, indicating that an apparent acid dissociation constant (pK_<app>) of FA extracted from landfilled MSWIR distributed with 2.84 (44%), 4.02 (34%) and 4.97 (22%). It was discussed about the landfill stabilization at an earlier stage considering on the existence of HSs from the results of sequential extraction of HSs in landfilled MSWIR and the mixture with composted sewage sludge.