MINERALOGICAL AND CHEMICAL-CHANGES IN MINERAL LINERS IN CONTACT WITH LANDFILL LEACHATE

The mineralogical and chemical integrity of mineral liners for domesti c waste landfill sites was investigated using a series of batch reacto r 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 r esults of the laboratory experiments are contrasted against those obta ined from samples of a 15-year-old mineral liner from a landfill site located near Stewartby, Bedfordshire. The interactions between a conce ntrated, ionic solution, such as a leachate, and mineral liners includ e ion-exchange, particle size reduction, mineral dissolution and clay- mineral disordering and collapse. Bentonites and high-swelling clays a re more susceptible to mineral transformations than mixed assemblage m udrocks and low-swelling clays. Understanding the interactions between leachate and mudrocks will assist the prediction of the long term per formance and integrity of natural lining materials.