Contaminant transport in a municipal solid waste landfill: On-site assessment and numerical modelling of vertical barrier wall effectiveness

Landfill-derived contamination remains a critical threat to environmental and public health. This study presents a novel integration of field investigation and multi-field coupling simulations to assess the performance of vertical barrier walls in mitigating both conventional and emerging contaminants at a municipal solid waste landfill in Southwest China. By combining on-site sampling of groundwater, surface water, leachate, and soil with finite element modeling, the study reveals alarming levels of pollution, including chromium (Cr) concentrations in soil exceeding regulatory limits by up to 13.3 times. More significantly, emerging contaminants such as antibiotics and hormones-sulfadiazine (up to 8.2 ng/L), sulfamethazine (up to 43.5 ng/L), ofloxacin, and estriol-were detected in both surface and groundwater, underscoring the inadequacy of conventional monitoring practices. The study further provides a comparative assessment of two vertical barrier configurations including geosynthetic clay liner-bentonite (GCL-B) and clay-bentonite (CLB), for the first time in the context of sulfadiazine transport. The GCL-B barrier exhibited superior containment, reducing pollutant flux by a factor of 6.01 and extending stabilization time sixfold compared to CLB. Transport analysis identified advection as the dominant mechanism, followed by dispersion, underscoring the critical role of hydraulic control in vertical barrier performance. This finding emphasizes the need for low-permeability, high-performance materials and site-specific hydrogeological assessments to ensure long-term containment. Collectively, this work provides new insights into landfill pollution dynamics and offers a scientifically grounded basis for optimizing vertical barrier design, especially considering the rising environmental relevance of emerging contaminants.