Advanced characterisation of groundwater contamination at a dumpsite: Methodology and assessment - Case study of a municipal solid waste dumpsite in India

Groundwater (GW) contamination due to municipal solid waste (MSW) disposal in open dumpsites is a pressing global issue. Traditional GW assessment studies are limited to single-depth sampling from nearby wells/handpumps, providing limited insights into subsurface soil characteristics and are prone to cross-contamination. The present study introduces an innovative methodology integrating advanced techniques: Cone Penetration Testing (CPT), Hydraulic Profiling Tool (HPT), Continuous Soil Sampling, and Discrete GW Sampling. Conducted at an operational dumpsite in New Delhi, India, from January to February 2023, the site investigation program covered seven distinct locations to incorporate the entire dumpsite area. The investigation proceeded in stages, starting with subsurface soil characterisation using CPT and HPT, followed by extracting soil and GW samples using CPT and HPT data. Due to restrictions in the northeast direction, GW samples were directly extracted from borewells. The results revealed maximum and minimum concentrations of 171 items/l and 26 items/l of MPs, while ionic concentration reached 13,200 ppm for Cl^- and 4437 ppm for SO₄^-2. A maximum of 0.721 ppm, 0.663 ppm and 0.948 ppm concentration was observed for Ni, Cu and Mo in GW samples. Spearman correlation and principal component analysis underscore the influence of Ec, TDS, Na⁺¹ and Cl^-1 on GW quality. This integrated approach effectively identifies high-permeability layers, which are crucial for understanding contaminant dispersion, and ensures precise sampling at various depths with minimal cross-contamination. This research demonstrates the proposed methodology's effectiveness in providing more profound and precise insights into GW contamination dynamics and suggests its utility in forming the basis for more effective remediation and regulatory strategies.