THE EFFECT OF INSIDE CIRCUMSTANCE OF THE HAZARDOUS WASTE LANDFILL ON THE LEACHING BEHAVIOR OF HARMFUL HEAVY METALS

In Japan, among three landfill classes, the hazardous waste landfill is used for disposing of hazardous waste of which leaching of heavy metal exceeds its criteria. To prevent the emission of a hazardous substance to the surrounding environment, the hazardous waste landfill is required to be constructed with a robust concrete wall and base, and the top must be capped. Because of the containment structure, rainwater infiltration and air intrusion hardly occur. This means the leaching potential of hazardous heavy metals in waste remains forever. But considering long term safety, their leaching potentials must be better reduced. In this study, the influence of interior condition in the hazardous waste landfill on the leaching of heavy metals was examined from the accelerated weathering experiments for dust which is disposed of at the hazardous waste landfill. As the results, a decrease in the leaching amount of Cd, Pb, Mn, and Zn was confirmed in a wet environment where adsorbed water was present on the particle surface. On the other hand, in the dry and CO2 saturated environment, an increase in the leaching amount was observed. The former phenomenon was thought to be the formation of hydroxide at the particle surface, and the latter was considered to be the influence of adsorption of CO2 to Fe3O4 and ZnO. Though further scientific verification is required for each phenomenon, the findings obtained in this study indicate that the leaching of heavy metals from wastes in the hazardous waste landfill may change over time depending on the interior condition.