Characterization of potentially toxic elements in leachates from active and closed landfills in Nigeria and their effects on groundwater systems using spatial, indexical, chemometric and health risk techniques.
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This study examines potentially toxic elements (PTEs) in leachates from three landfills (active and closed sites) to quantify and compare their degree of toxicity and percolation effects on aquifer groundwater based on distance zonation. The finding revealed that the active landfill leachates had higher concentrations (P < 0.05) of PTEs, with EC, TDS, Cd, Cu, Fe, Zn, Pb, and Mn being above the standard limits for wastewater. The leachate pollution index confirmed high toxicity of the active sites. The geospatial maps suggest that the aquifer was influenced by leachate migration effects, with the groundwater situated within 100 m of the landfills exceeding the regulatory limits. Based on the Ficklin-Caboi assessment, the groundwaters were categorized into "low metals-near neutral" and "high metals-near neutral." The contamination degree, heavy metal contamination index, groundwater quality index, and water pollution index denote that over 40% of the groundwaters are "highly to extremely" polluted and are unfit for drinking, while over 50% are "excellently pure." The geospatial maps revealed that all the groundwaters within 100 m of the landfills are polluted, especially those near the active landfills. The prevailing factors impairing the quality of groundwater were Pb > Cd > TDS > Fe > EC > Cr > pH > Mn > Se > Co. The correlation coefficients, principal components, and cluster analyses confirmed the heterogeneous nature of the landfills and that the solid wastes were mainly from industrial, commercial, and household sources. Aside from the migration effect of leachates, other anthropogenic and geological factors are influencing the aquifer systems. The health risk assessment showed that the groundwaters within 100-500 m of the landfills are capable of causing noncarcinogenic and cancer health risks in exposed populations, with children and those within the distance of 100 m being the most vulnerable groups.