Effect of temperature on diffusion leaching characteristics of clays containing geogenic substances

This study focuses on how diffusion leaching characteristics of heavy metals in clay are influenced by the changes in ground temperature caused by geothermal heat utilization. Diffusion tests were conducted on clays containing geogenic heavy metals and using temperatures of 10, 20, 35, and 50°C. The results showed that diffusion leaching increased with elevated temperatures and lower dry densities. Diffusion coefficients calculated using total content and initial pore water concentration, respectively, were compared, and the latter was found to reflect the effect of temperature better. Furthermore, it was suggested that the viscosity of the pore water might be a factor affecting the temperature dependence of the leaching flux. The results indicate the importance of safety assessment for the introduction of geothermal technology, taking into account the effects of temperature and clarifying the acceptable temperature change.