Transport of typical chlorinated hydrocarbons in soils: Transport behavior, phase distribution, sensitivity analyses

• The phase distribution of three CHCs in various soils was first investigated. • A numerical model was constructed to simulate dissolved-phase CHCs transport in soil. • Sensitivity analysis identified key parameters and CHCs' coefficients were compared. • The study's value for CHCs phase distribution in soil remediation was discussed. Chlorinated hydrocarbons (CHCs) are toxic, insoluble, resistant to degradation, and commonly found in soil, posing risks to human health and environmental safety. This study constructed six soil column models to simulate the migration and distribution of CHCs in soil, and their migration pathways and sensitivity parameters were investigated by numerical simulation, to assess contamination levels at a polluted site. The results showed that the penetration time of CHCs across different soil columns followed this order: clay column > (loam + clay) column > loam column > (loam + clay + sand) column > (loam + sand) column > sand column. Among the CHCs, 1,2,4-trichlorobenzene had a significantly longer penetration time compared to chlorobenzene and carbon tetrachloride. CHCs were mostly present in the free-phase (∼50 %) of the soil columns, while carbon tetrachloride was mainly in the gas phase (∼28 %), 1,2,4-trichlorobenzene in the residual phase (∼35 %), and chlorobenzene in the dissolved phase (∼25 %). Sensitivity analysis revealed that density, dispersion coefficient, and linear adsorption coefficient were the most sensitive parameters influencing CHCs transport, while porosity and permeability had minimal impact. 1,2,4-trichlorobenzene showed the highest sensitivity, followed by chlorobenzene, and then carbon tetrachloride. This study provides valuable insights into the migration patterns and phase distribution of CHCs in soil, which can help predict contamination levels at real sites and assess ecological risks. The findings offer an important theoretical basis for optimizing remediation technologies and improving pollution control and risk assessment strategies.