Evaluation of heavy metal content and potential ecological risks in soil samples from wild solid waste dumpsites in developing country under tropical conditions

Solid waste management constitutes a major concern and unresolved problem in most parts of the world, particularly in developing countries where solid waste is disposed in unregulated dumpsites in the public spaces. This practice can lead to contamination of environmental compartments such as soil, surface and groundwater which could negatively impact human health. In this study, surface soil samples were collected from 15 selected solid waste dumpsites in Kinshasa City (Democratic Republic of the Congo) to examine the heavy metal content and potential environmental risks. The results highlighted a high concentration of metals in soil samples compared to local background values and international threshold. The average concentration of metals in all soil samples followed generally the order: Zn>Pb > Cu >Cr> Co> Cd> As> Hg. The calculated pollution indexes including Geo-accumulation, Enrichment Factor, Contamination degree and Potential Ecological Risk, revealed polymetallic contamination dominated by several of these metals in which Zn, Cu, Pb and Hg were of greatest concern indicating high environmental risks. This work showed that illegal wild landfills represent a real danger for the environment and human health. Due to the toxicity of heavy metals, the measures to establish a monitoring program that address uncontrolled landfills and solid waste management and disposal are recommended to reduce the load of contaminants in soils which can reach surface and groundwater. On the other hand, the use of manures from these dumpsites for agricultural purposes should be discouraged because they may be easily absorbed at alarming levels by vegetables.