Effects of mining on physicochemical properties of soil and water at Ofiki gemstone mining site, southwestern Nigeria

The global demand for jewellery and precious stones has contributed to the recent growth in gemstone mining and its industry. While this trend is expected to soar in the coming years, a proper assessment of the environmental effects of gemstone mining is required to prevent further ecosystem degradation. This study assessed the impact of mining on the soil and water at the Ofiki gemstone mining site in southwestern Nigeria. Soil and water samples were collected from the mining site and the adjoining undisturbed areas. The physicochemical properties of the samples were analysed using standard procedures, and the results were compared with the World Health Organization (WHO) and other standard threshold limits. The results indicated that mining at the site caused a substantial loss of soil organic matter, nitrogen and potassium necessary for plant growth. Furthermore, the soil around the mining site was highly acidic, with low macronutrient concentrations in and around the site. Additionally, surface water at the mining site was highly acidic, with phosphate and iron concentrations exceeding WHO permissible limits. However, other physicochemical properties of the water samples in and around the mining site were within WHO permissible limits.