Evolution Characteristics and Mechanisms of Thermal Conductivity of Diesel-Contaminated Soil Under High Temperature

Thermal desorption remediation technology is extensively utilized in organic-contaminated sites.A comprehensive understanding of the thermophysical properties of contaminated soils is essential for improving pollutant removal efficiency and minimizing energy consumption.This study examines the thermal conductivity behavior of Nanning alluvial clay over a temperature range of 20→400℃,considering varying water and diesel contents,using the probe method.Subsequently,using various analytical instruments,this study further elucidates the mechanisms by which diesel storage state,particle size distribution and pore structure influence the thermal conductivity of soil.The results indicate that at room temperature,diesel increases the thickness of the adsorption layer on soil particles surfaces and enhances the effective contact area between particles.As a result,the thermal conductivity of soil increases with rising oil content (from 0 to 7.0%) at lower water contents (1.2%,6.2% and 11.2%).In contrast,at higher water contents (16.2% and 21.2%),diesel replaces the binding water around the particles,leading to a reduction in thermal conductivity with increasing oil content.The thermal conductivity of soils decreases significantly when 20→100℃ due to the evaporation of water or partial removal of diesel.In uncontaminated soil,thermal conductivity shows a moderate increase when 100→400℃,attributed to the growth in soil particle size and enhanced thermal motion.For diesel-contaminated soil,the thermal conductivity lightly diminishes when 100→300℃ stemming from pyrolytic carbon formation and increased porosity,while minimally increases when 300→400℃ as a consequence of pyrolytic carbon removal.