Mapping heavy metal contamination in soils around Ikpeshi marble mining sites in Southern Nigeria using the regression kriging spatial prediction approach

Determining the geospatial distribution and level of heavy metals (HMs) pollution in the soil is crucial for the management and restoration of heavy metal-polluted soils around mining sites. This study analyzed the content of heavy metals (HMs) such as arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni), zinc (Zn), and iron (Fe) in soils around the Ikpeshi marble mining sites in Southern Nigeria. The degree of contamination and several pollution indices, including enrichment, contamination, and geo-accumulation index, were calculated to assess the soil contamination level around the marble-mining sites. Average concentrations of As, Cd, and Cu exceeded Clarke’s and crustal values, indicating significant contamination near mining sites. Cd ranged from 0.01–12.8 mg kg⁻¹ (mean 4.7 mg kg⁻¹), and Cu from 0.09–84.6 mg kg⁻¹ (mean 31.0 mg kg⁻¹). Metal concentrations decreased with distance from mining activities, confirming their anthropogenic origin. Overall, soils were highly to extremely contaminated with Cd, highly contaminated with Cu and As, moderately contaminated with Pb and Zn, and uncontaminated with Fe, Ni, and Mn. Contamination ranked as Cd > Cu > As > Pb > Zn > Fe > Ni > Mn. This study offers a strong scientific foundation for the clean-up and management of heavy metal-contaminated soils in marble mining regions of Nigeria.