Evaluation on Potential Use of Ariake Clay in a New Barrier System

This study presents an assessment of the use of a typical Japanese marine clay, Ariake clay, as a soil barrier and its application in a new proposed soil barrier system. Two types of heavy metals, Cd²⁺ and Pb²⁺, are selected as key contaminants for laboratory diffusion testing. Using a commercially available contaminant transport software, the diffusion coefficients and partition coefficients were back-calculated from the results of the diffusion test. The diffusion coefficients are found to be consistent with previously published values. The lab test data were applied for evaluating the performance of a new barrier system in which the Ariake clay is utilized. Numerical analyses of contaminant transport through the barrier are performed to characterize the temporal variation in concentrations and mass flux of Cd²⁺ and Pb²⁺ in the aquifer underlying the landfill. The results show that within the long-term post-closure period, the concentrations of Cd²⁺ and Pb²⁺ were much lower than those regulated by the Japanese government, indicating that the new barrier system is effective. By parametric analysis, some factors controlling the performance of the proposed soil barrier system are discussed. Design parameters are recommended for practice.