Heavy Metal Release Potential of Selected Dumpsite Waste Streams: Geochemical Evidence and Assessment of Soil Pollution Indices

Abstract

The release of potentially harmful metals from waste materials into soil represents a significant pathway for soil contamination. This study quantitatively examined the release potential of metals (Cd, Cr, Ni, Pb, and V) from diverse waste streams at predetermined depths (0–20 cm and 20–40 cm). The principle of mass balance was employed to assess waste-metal release potential, with contamination factor (CF), metal pollution index (MPI), and pollution load index (PLI) employed as pollution indicators. Findings indicated that the investigated wastes caused significant pollution within the studied soils, with automechanic- and paint-related wastes having the highest metal-release potentials. The mean natural background concentration of lead in the studied soils was 7.0 mg/kg. Automechanic wastes elevated this concentration by 529 times, while paint- and abattoir-related wastes increased it by 197 and 8.4 times, respectively. CF values across the investigated dumpsite soils and depths revealed severe contamination, particularly for chromium, with values reaching 972.36. MPI values indicated substantial multi-metal contamination, with a PLI peak of 292.58. High contamination levels were not confined to the topsoil, as some locations recorded elevated concentrations of Pb and Cr at 20–40 cm depth, suggesting either downward migration of the contaminants through the soil profile or burial of originally contaminated topsoil during land filling. All affected soils showed excessive pollution, while the different waste streams exhibited varying capacities to release heavy metals into soil. These results underscore the need for source-specific waste management and improved strategies to mitigate ongoing contamination and associated risks.