Spatial distribution and potential ecological and health risks associated with heavy metals in the Ijero-Ekiti mining site, Nigeria

Abstract

Artisanal gold mining, a labor-intensive and antiquated technique, is a growing industry and the source of income for rural communities all over the world. However, artisanal gold mining has potential negative and long-term effects on economy, environment, and society. This study collected soil samples from 16 sample points including a control point to examine the pollution degrees and spatial distribution of heavy metals, as well as ecological and health risks associated with heavy metal pollution in the Ijero-Ekiti mining site, Nigeria. Geographical Information System (GIS) and remote sensing technologies were used to identify regions with high concentrations of heavy metals and assess the environmental impact of gold mining activities. The results show that the mean heavy metal concentrations of 16 soil pointa are 8.94 (±5.97) mg/kg for As, 0.18 (±0.54) mg/kg for Cd, 0.11 (±1.06) mg/kg for Co, 14.32 (±3.43) mg/kg for Cr, 6.89 (±0.64) mg/kg for Cu, 48.92 (±11.77) mg/kg for Fe, 135.81 (±30.75) mg/kg for Mn, 5.92 (±0.96) mg/kg for Ni, 5.72 (±1.66) mg/kg for Pb, and 13.94 (±1.38) mg/kg for Zn. The study reveals that heavy metal concentration in soils follows the order of Mn>Fe>Cr>Zn>As>Cu>Ni>Pb>Co>Cd. An analysis of soil samples indicates that 3 principal components (PCs) account for 70.008% of the total variance and there are strong positive correlations between various pairs of heavy metals. The total potential ecological risk index (309.599) in the study area is high. Non-carcinogenic risk suggests that there may be long-term health impacts on people who work in the mining areas due to chronic exposure to the environment. Based on the study, the hazard index of carcinogenic health risks associated with heavy metals through ingestion is 520.00×10^–4. Dermal contact from As and Cr also increases the risk of cancer, with the highest hazard index value of 18.40×10^–4. The lowest exposure pathway, with the hazard index value of 0.68×10^–4, indicates that the inhalation of heavy metals has a comparatively low risk of cancer. This study recommends the formulation of policies to monitor the Ijero-Ekiti mining site and other regions in Nigeria where indiscriminate artisanal gold mining activities exist.