An Integrated Framework Incorporating Multi-Models for Assessing the Fate of Heavy Metals from Sanitary Landfills to the Subsurface Media

This study presents an integrated framework for assessing the potential contamination risks beneath sanitary landfills, focusing on the migration of heavy metals through subsurface media. The study explores how varying landfill conditions influence the migration and lifespan of heavy metals in the subsurface environment. Research objectives included developing a comprehensive approach to assess contamination risks by integrating leachate generation, contaminant lifespan estimation, landfill service life, subsurface soil properties, and contaminant transport modelling. The methodology incorporates advanced modeling tools: the HELP model estimated leachate generation rates, the Rowe model evaluated contaminant lifespan and concentration changes, and COMSOL simulated transport through landfill liner and the unsaturated zone. Various scenarios were simulated, including different leachate generation rates, contaminant types, and landfill service life. Simulations revealed that higher leachate generation rates and initial contaminant concentrations significantly reduced pollutant lifespan. Heavy metals exhibited distinct leaching behaviors, with Cd, Cu, Hg, Ni, and Zn more prone to migration than Cr and Pb. COMSOL modeling highlighted the importance of effective landfill design, demonstrating that inadequate liners increase leachate penetration and environmental risks. The findings highlight the necessity of high-adsorption, low-diffusion liners, regular leachate monitoring, and system maintenance to minimize groundwater contamination. The novelty of this work lies in its integration of established models (HELP, Rowe, COMSOL) using minimal site-specific inputs, such as grain size distribution and groundwater depth, offering a streamlined approach for proactive landfill site selection and risk management. This framework provides a practical tool for evaluating landfill performance and ensuring long-term environmental sustainability.