Spatial assessment of landfill leachate-induced groundwater contamination using hydrogeochemical and GIS techniques

This study aimed to evaluate the impact of landfill leachate on groundwater quality around the Mehmood Booti and Saggian municipal solid waste disposal sites in Lahore, Pakistan, using hydrogeochemical investigations and GIS-based spatial analysis. Groundwater samples were collected from boreholes located in downslope areas identified through an inverted watershed approach during pre-monsoon and post-monsoon seasons. Major physicochemical parameters, including pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness, turbidity, calcium (Ca), magnesium (Mg), chloride (Cl⁻), bicarbonate (HCO₃⁻) and dissolved oxygen (DO) were analyzed following standard methods. The results demonstrated significant seasonal and spatial variations in groundwater quality. Pre-monsoon samples exhibited elevated EC, TDS, hardness, Cl⁻, HCO₃⁻, Ca and Mg concentrations due to reduced dilution and enhanced leachate influence. Statistical analysis using one-way ANOVA revealed significant seasonal differences for EC, TDS and Cl⁻ in Mehmood Booti, while pH and TDS showed significant variation in Saggian (p < 0.05). GIS-based spatial interpolation identified contamination hotspots near landfill sites, indicating leachate migration toward nearby groundwater systems. The localized increases in EC and hardness suggested site-specific groundwater deterioration. The findings highlight the influence of landfill leachate on groundwater hydrochemistry and emphasize the need for continuous groundwater monitoring, effective landfill management and improved leachate control strategies to protect groundwater resources in urban environments.