Contaminant migration in vadose zone beneath unregulated landfills with damaged geomembranes

A one-dimensional analytical model was developed to simulate the migration of organic contaminants from an unregulated landfill through a damaged geomembrane into the underlying unsaturated soil. The model integrates both geomembrane defects (e.g., wrinkles, holes) and unsaturated soil properties, and an analytical solution for contaminant concentration (as a function of time and depth) was derived using boundary transformation, the shift theorem, and Laplace transform/inverse transform. Parametric analysis of five key factors showed: (1) Increases in geomembrane wrinkle size, hole number, and soil saturated water content significantly accelerated contaminant transport, deepened migration depth, and elevated risks to subsurface ecosystems and groundwater; (2) A higher soil unsaturated exponent markedly delayed migration and inhibited vertical penetration. Notably, unregulated landfills in high-saturation, low-unsaturated-exponent regions (e.g., coastal areas) face heightened contamination risks. This model provides a practical tool for predicting contaminant behavior and supporting environmental risk assessments, directly enhancing the management of containment systems in unregulated landfills.