Characterization and pollution risk assessment of landfill-mined fine fraction: a case study from Guwahati, India

Landfill mining addresses the issue of legacy waste while recovering secondary resources. The soil-like material or landfill-mined fine fraction (hereafter LMFF) is one of the principal residues of landfill mining and makes up approximately 45-80% of the total landfill-mined residues. Because of the unique waste composition and the improper practices of dumping mixed MSW, it is crucial to undertake characterization studies on LMFF worldwide. This study examines LMFF obtained from the Boragaon dump site in Guwahati, India. The analyses included geotechnical, physico-chemical, and heavy metal characterization along with their bioavailability and leachability. The sequential extraction and pollution indices were also evaluated for LMFF. The results classified the LMFF as well-graded non-plastic sand with high porosity (69%) and low values of specific gravity and bulk density (2.15 and 1.01 g/cm³, respectively) owing to organic matter. LMFF contained a high amount of macro-nutrients (NPK), total organic carbon (10.2 ± 0.2%), and volatile content (18.3 ± 0.4%) comparable to those of city compost. LMFF also exhibited elevated measures of total heavy metals. Cu, Zn, Mn, and Fe had the highest potential to enter the food chain and impact biodiversity, with Mn being the most mobile. Appropriate treatment and utilization methods have been suggested, considering the evident potential of LMFF to cause pollution within the geoenvironment.