Open access publications in the SLU publication database

Abstract

In Sweden, a large number of closed landfills containing a mixture of household waste and waste from industries and other sources exist. These landfills originate from a time when regulations were less strict and contain large amounts of organic material derived from household waste, plus large amounts of metals. This partly decomposed organic material can contribute to the stability of the landfill by retaining metals. When landfills are closed they are covered to create strictly anaerobic conditions. Over time, oxygen can be expected to penetrate the landfill mass as oxygenated rainwater and atmospheric air. This will affect the deposited organic material and the leaching pattern. The present study examined the ageing processes in landfills and the environmental impacts of these by characterising the content of metals, organic material and water. Artificially aged and original landfill material were analysed to determine changes in metal binding forms, cation exchange capacity and Cu2+ ion-binding ability. Changes in the concentration of dissolved organic matter in the aqueous phase due to aeration were analysed. The proton-binding and Cu2+-binding capacity of dissolved organic material was investigated by titration analysis. Metal retention ability was determined in column experiments. Ageing of the landfill material increased the cation exchange capacity and the ability to bind Cu2+. The column experiment revealed that the metal-binding ability of both original and aged material was good. Ageing of the landfill material caused a decrease in the dissolved organic carbon content and thus a lack of metal-transporting ligands. Metal stability in the landfill was controlled by the pH and redox potential and by the organic matter content. Stabilisation of organic material to humic-like substances and formation of charged oxide surfaces with good metal-binding ability will be important for future landfill oxidation, whether natural or forced.