The migration of groundwater flow and contaminants in fractured medium is complicated owing to the strong heterogeneity and anisotropy of fractured rock mass. Taking the environmental restoration and groundwater protection of the Lishui domestic waste landfill in Nanjing as the background, the groundwater environmental impact assessment and prediction are conducted for the groundwater environmental pollution that may be caused by the leakage of the landfill leachate after the closure of the domestic waste landfill. The strata of the landfill site are clay-cobble gravel, strongly and moderately weathered breccia, with obvious anisotropy and significant differences in rock mass permeability. A 3D numerical model of groundwater flow and contaminant migration in the landfill area is established by integrating the hydrogeological field tests and a conceptual model in the study area. Based on the parametric inversion method, the heterogeneous anisotropic permeability coefficient of the fractured medium is calibrated, and the temporal and spatial migration characteristics of contaminants such as ammonia nitrogen and mercury are predicted using the corrected model under the normal and failure conditions of the antiseepage curtain. The calculated results show that when the antiseepage fails, the maximum migration distances of contaminants in the horizontal direction after 100 days in the old and new landfills are 7.66 m and 15.64 m, respectively, and the maximum migration distances after 20 years are 192.5 m and 113.89 m, respectively. The migration direction and distances of contaminants are consistent with the hydrogeological conditions of the study area. The model calculation results provide a corresponding basis for the antiseepage control of contaminants.

The influence of soil water content and contaminant injection pressure on the migration behaviour of p-Xylene (one of the organic pollutants in Benzene Toluene Ethylbenzene & Xylene) is investigated in the unsaturated zone using the controlled laboratory sandbox experiments. The results show that, at equivalent migration distances, higher soil water content leads to longer migration durations and reduces transport velocities, whereas greater injection pressure promotes faster contaminant movement. These findings highlight the governing role of water saturation in the water–oil–gas three-phase system, in which increased water content decreases the relative permeability of the oil phase and retards capillary-driven BTEX transport. Unlike many previous studies in which contaminants commonly migrate downward toward the groundwater table, the BTEX in this study did not reach the water table and exhibited partial upward migration. Overall, the results provide experimental-scale insight into key mechanisms governing BTEX transport in unsaturated sandy media and serve as a reference for improving predictions of contaminant fate and migration pathways in field settings.