Effects of thermal desorption temperature up to 500 °C on the thermophysical properties and fertility of soil in organic-contaminated sites

• Soils were sampled from organic-contaminated sites adopted for TD remediation. • Soil thermal properties were measured by a self-developed sealing apparatus. • Soil fertility properties after thermal treatment up to 500 °C were investigated. • Crop cultivation experiments were carried out for vivid auxiliary characterization. • The variations of fertility and thermal properties with temperature were discussed. High-temperature thermal desorption is effective for remediating organic-contaminated sites, but its damage to soil functions and high energy consumption raise concerns. In this work, the variation of fertility indicators of two soils with thermal treatment temperature was investigated experimentally. To overcome the difficulties in measuring soil thermophysical properties under sealing and high-temperature conditions, two apparatus matching with the Hot Disk device were established and by which massive data were measured. The results show that, as temperature rises up to 500°C, the combustion and decomposition of organic components and soil minerals gradually enhance, leading to a decrease in most fertility indicators, but an increase in grain size and pH. Available phosphorus and exchangeable potassium decrease with temperature rise first, but increase over 400°C. Soil thermal conductivity and specific heat are positively correlated with temperature and water content. Water diffusion will intensify over 40∼60°C, leading to an intense increase in soil thermal conductivity. The results are expected to provide data basis and theoretical guidance for the comprehensive consideration of remediation effects, land reuse, and energy consumption in practical applications of thermal desorption remediation.