This thesis describes the chemical, mineralogical and spatial characterisation of a new cell of engineered Oxford Clay in an existing landfill site. The clay content, organic carbon content, soil pH, cation exchange capacity and exchangeable cations were determined for 35 samples taken from the bottom of the cell. Three elements Cr, Cu and Zn were also determined in fractions bound to carbonates, Fe-Mn oxides, organic matter and exchangeable sites as well as total concentrations in the compacted clay used as liner. These elements were characterised in the soil solution as well. Stability diagrams were used to identify which inorganic species would be in the soil solution. Inorganic species were quantified using the geochemical equilibrium model, Geochem-PC. Geostatistics were used to describe the spatial variability of the soil pH, organic matter and metals bound to soil solid phases. Variograms were calculated using Variowin 2.1; the ordinary kriging and crossvalidation process were carried out using Gslib. It was possible, through the chemical, mineralogical and spatial characterisation, to identify the presence of a layer rich in pyrite underneath the liner system The spatial characteristics of the landfill cell are complex and to a large extent are associated with the mineralogical composition of the site, particularly with the oxidation of pyrite in the surface, that causes the pH to be low. pH spatial variation correlates with the distribution of Cu, Cr and Zn in the soil.
This work shows that it is possible to predict the behaviour of trace elements through the characterisation of geochemical parameters; even more, the mineral, chemical and spatial characterisation of geochemical parameters in a clay liner can reveal trends and natural hazards in a landfill site, and could be used to reduce risks and optimise the monitoring designs.