Bioremediation of potentially toxic metals (PTMs) from dumpsite soils using the composts of Jatropha curcas and Ficus exasperata.

Soil pollution by potentially toxic metals (PTMs) poses a major environmental and public health challenge in developing countries, particularly due to inadequate waste management practices at urban dumpsites. These PTMs persist in the environment, accumulate in the food chain, and threaten ecosystem integrity and human health. Despite the growing concern, sustainable and affordable remediation strategies remain underexplored. The present study aimed to remediate PTMs (Cd, Cr, Cu, Fe, Mn, and Pb) in dumpsite soils using composts derived from Jatropha curcas and Ficus exasperata. Before soil remediation, two different composts were formulated by combining leaves of Jatropha curcas and Ficus exasperata with poultry manure and sawdust over a nine-week period. Polluted soils from three major dumpsites in Ogun State were collected and treated with stabilised compost for six weeks in a pot experiment. A complementary remediation strategy was introduced using castor oil plants. Physical and chemical constituents of soil and compost samples were monitored using standard methods. Compost and soil data were subjected to both descriptive and inferential statistical analysis. The study also evaluated removal efficiency and pollution index of PTMs in polluted and treated dumpsite soils. Results indicated that the dumpsite soils from Ota had the highest levels of all the observed PTMs except manganese, which dominated the samples from Ijebu-Ode. After the bioremediation experiment, Jatropha and Ficus composts were able to remove a significant amount of PTMs from the dumpsite soils in the following order: Cd (71 ± 11%) > Cu (70 ± 16%) > Mn (67 ± 9%) > Cr (59%) > Fe (53 ± 25%) > Pb (52 ± 17%).