The paper discusses the mineralogical and chemical stability of the Oxford Clay as a landfill liner for the containment of domestic waste. The results from a series of batch equilibrium experiments with the mudrock and a synthetic leachate are compared with samples of a liner cored from a 15‐year‐old site in the Formation. The effects of leachate on the Clay include mineral dissolution, exchange of cations, particle‐size reduction and collapse of illite‐smectite. In situ mixed‐assemblage mineral liners, such as the Oxford Clay, are capable of attenuating leachate components and buffering acid leachates whilst the predominant clay minerals, i.e. illite and kaolinite, remain stable. Alterations to the mineralogy and chemistry of the samples resulting from both short‐term and long‐term exposure to leachate are discussed with reference to the implications to landfill practice.
The mineralogical and chemical integrity of mineral liners for domestic waste landfill sites was investigated using a series of batch reactor experiments. A synthetic acetogenic leachate was developed based on the composition of domestic waste leachates. The interactions between the synthetic leachate and mudrocks used by Shanks and McEwan Ltd. to line landfill sites located in the United Kingdom are described. The results of the laboratory experiments are contrasted against those obtained from samples of a 15-year-old mineral liner from a landfill site located near Stewartby, Bedfordshire. The interactions between a concentrated, ionic solution, such as a leachate, and mineral liners include ion-exchange, particle size reduction, mineral dissolution and clay-mineral disordering and collapse. Bentonites and high-swelling clays are more susceptible to mineral transformations than mixed assemblage mudrocks and low-swelling clays. Understanding the interactions between leachate and mudrocks will assist the prediction of the long term performance and integrity of natural lining materials.
Compacted clay liners are common, major, components of landfill leachate (fluid) containment systems. This is sensible, but knowledge and understanding of the longterm performance and behaviour of day mineral/landfill leachate systems remain very limited. The authors studied the reactions of day soil with leachate simulants related to three different climates and waste cultures. The day came from a Tertiary sequence near Melbourne, Australia, a type in common use locally for landfill engineering. X-ray diffraction was used to observe mineralogical change in 3 mm clay plugs caused by reactions with the leachate simulants. Changes in hydraulic conductivity were also measured. The results show both that the different leachates have distinct effects on the clay minerals, and that the leachate/day reactions have direct measurable and distinct impacts on hydraulic conductivity. The laboratory studies were completed at the University of Melbourne. The X-ray diffraction work was completed at The Natural History Museum in London. The experimental results are discussed here and indications given of some potential implications.
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