The application of persulfate (PS) for the remediation of petroleum hydrocarbon contamination is among the most widely employed in situ chemical oxidation (ISCO) techniques, and it has received widespread attention due to its limited impact on soil integrity. This study employed a FeSO4-activated PS oxidation method to investigate the feasibility of remediating soil contaminated with total petroleum hydrocarbons (TPHs). The factors tested included the TPH concentration, different PS:FeSO4 ratios, the reaction time for remediation, soil physical and chemical property changes before and after remediation, and the effect of soil before and after remediation on soybean growth. The TPH degradation rate in soil was highest for high-, medium-, and low-TPHs soils-81.5%, 81.4%, and 72.9%, respectively, with minimal disruption to the soil's physicochemical properties-when PS:FeSO4 = 1:1. The remediation verification results indicated that the condition of the soybeans was optimal when PS:FeSO4 = 1:1. Under this condition, the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate all remained high. Therefore, the best remediation effect was achieved with PS:FeSO4 = 1:1, which also minimized the damage to the soil and the effects on crop growth.

The permeability of treated contaminated soil is an important factor to consider when reusing polluted soil in engineering projects. In this study, lime and fly ash were chosen as solidification materials due to their ability to both adsorb and solidify contaminants. The permeability coefficients of petroleum-contaminated soil before and after solidification, as well as the residual petroleum content within the soil, was investigated under varying parameters such as confining pressure, osmotic pressure and contamination intensity. X-ray diffraction and scanning electron microscopy were used to analyze the evolution of permeability and the migration and diffusion patterns of pollutants, providing insights into the engineering reutilization potential of solidified petroleum-contaminated soil. The results showed that the adsorption effect of the solidified product on petroleum molecules weakened the hydrophobicity of the petroleum, increasing the effective permeation pathways in the soil. The permeability coefficient of solidified petroleum-contaminated soil was two orders of magnitude higher compared to unsolidified soil. Both solidified and unsolidified petroleum-contaminated soil exhibited decreased permeability due to the enhanced adsorption and interception capacity of the soil matrix for petroleum, as well as the elevated confining pressure, osmotic pressure, and contamination level, which intensified the interception among soil particles. The solidification process effectively controlled the migration and diffusion of petroleum contaminants under permeation conditions. The residual petroleum content in various locations closely approximated the initial content, reducing the risk of pollution through permeation. Considering the mechanical properties (compressive strength of 1 280.1 kPa, shear strength of 388.88 kPa), permeability (ranging from 4.28x10(-6) cm/s to 7.39x10(-6) cm/s), and migration control characteristics (fluctuation rate from 0.3% to 4.9%) of lime and fly ash, it can be concluded that lime and fly ash solidified petroleum-contaminated soil can be reused in the construction of subgrade materials that require impermeability.