Effects of high temperatures on soil properties: lessons to share from smouldering remediation experience

Aggressive, high-temperature contaminant remediation processes such as smouldering remediation are growing in popularity as technical knowledge of their capabilities becomes more widespread. Smouldering remediation is most aggressive of these processes and exposes soils to temperatures across the range of 500-1000 oC for hours to days, displacing water and destroying in excess of 99.9% of contaminant mass. The high temperatures and aggressive chemical reactions result in significant changes to the soil properties, particularly at the particle surface. Shifts in soil geochemistry, mineralogy, and structure are observed. Micro computed tomography shows that grain surfaces become significantly smoother after remediation. The changes are more extensive than initial mineralogy testing had suggested. Increased smoothness affects grain-grain and grain-water interactions and may explain some of the dynamic changes in infiltration, permeability, cohesiveness, and strength that have been observed in soils after smouldering remediation. Understanding these effects is essential to link micro-scale changes to macro-scale behaviour and develop a holistic approach to contaminated soil remediation and reuse. Important analogies can be drawn to the effects of fires on soil properties.