Waste Fingerprints in Soils: A Study of the Influence of Wastes on the Concentrations of Selected Heavy Metals in Soils Underlying Open Dumpsites

Abstract

Sustainable waste management and heavy metal pollution are among the most urgent environmental challenges globally. When waste becomes a source of heavy metals in soils, the problem becomes more complex and requires integrated management solutions. This study examines the proportion of heavy metals released from automechanic, paint processing, and abattoir wastes into the underlying soils. Samples from waste piles were collected from dumpsites, along with soil samples from beneath them, which were analyzed for levels of selected heavy metals, including lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni), and vanadium (V), using standard laboratory procedures. Soil samples were digested with Aqua regia and analyzed for Pb, Cd, Cr, Ni, and V via atomic absorption spectrophotometry. The heavy metal release percentage (HMR) was calculated based on the principle of mass balance. Results showed that Pb (8621.1 mg/kg), Cd (1413.1 mg/kg), Ni (563.0 mg/kg), and V (507.0 mg/kg) were highest in automechanic wastes, while Cr (1413.1 mg/kg) peaked in paint processing wastes. Similarly, automechanic waste dumpsites had the highest concentrations (mg/kg) of Pb, Cd, and Ni at 4310.0, 179.0, and 303.0, respectively, while paint-impacted soils had concentrations of 600.0 and 240.0 mg/kg for Cr and V. The HMR values were 49.8 for Pb, 41.7 for Cd, 42.7 for Cr, 51.8 for Ni, and 48.6 for V. Transferring these hazardous substances from contaminated wastes to the soil poses risks to the ecosystem. The levels of Pb, Cd, Cr, Ni, and V exceeded their respective limits for residential zones set by FAO by 1437%, 3480%, 200%, 160%, and 1%, respectively, causing contamination of the pedosphere and disrupting its balance. Therefore, it is essential to adopt timely interventions to reduce risks through sustainable waste management policies and eco-friendly remedies such as phytoremediation.