Assessment of metal contamination in soil and plants from abandoned secondary and primary goldmines in Osun State, Nigeria

Abstract

Heavy metal contamination of soil, water, and crops, and their health impact on residents, is a persistent social issue, and several studies have identified health risks of residents living near abandoned mines. In this study, the heavy metal concentrations in the soil and plants of abandoned gold mines of the primary goldmine and the secondary goldmine, Ilesa-Osun State Nigeria of latitude 7°, 27’N to 7°,35’N and longitude 4°, 47’E to 4°,53’E was investigated. A total of 20 soil samples in replicates of two [both surface (0 to15 cm) and subsurface (15 to 30 cm)] were collected from both sites and eight plant samples were also collected from both sites for this study. Metal concentration was determined using the Inductively Coupled Plasma/ Optical Emission Spectrometry (ICP/OES) technique. The trend of metal concentration was, Cr >Zn >Cu >Co >Pb >As >Cd. Soils in the secondary goldmine had mean values for Cu, Cr and Co higher than NCI standards for soil, which is indicative of Cu, Cr Co contamination in general. Chromium concentration of 79.4 mg/kg was observed in the soils of the secondary goldmine indicating chromium toxicity, at both 0 to 15 cm and 15 to 30 cm depths. While in plants, metal concentration was Zn >Cu >Pb> Cr >Co >As >Cd >Cd. Cd. Cu and Zn contamination in plants from the primary goldmine, were above the normal concentration of metals found in plants, with Cu considered to be at a high level, also (21 mg/kg). The plants considered in this study were observed to have high potential for phytoextraction of certain heavy metals. Key words: Heavy metals, goldmines, contamination, soil, plants